Personally, I've always viewed Pidgeot as an above-average wallbreaker which has qualities that push it over the top and give it overbearing effectiveness on next-to-every playstyle currently employed in the tier- its 121 speed tier give it free reign speed-wise over almost the entire tier, and only Scarf users + the few pokemon that do sit above that speed tier (Mega Aerodactyl, Mega Beedrill, Mega Sceptile, to name a few) can outrun Pidgeot. The speed tier to me is the least broken part of Pidgeot and the part that should be focused on the least when considering Pidgeot's banworthy aspects, as even a great speed tier doesn't give it complete invulnerability to priority moves like Mazz named above. Mamoswine, Lucario, Entei, Machamp, Infernape, and the likes can all pick on Pidgeot's less-than-magnificient bulk and use it to their advantage, although Mega Pidgeot isn't going to be OHKO'd by any priority move anytime soon. It is realistic, however, to assume that throughout the course of the match chip damage and Stealth Rock damage is going to wear down Pidgeot and force it into range by these Pokemon, which does help to balance out Pidgeot's speed aspects.
To focus on another issue, Pidgeot also packs STAB Hurricane, which to me is the most broken aspect of Pidgeot's existence in the tier. Hurricane is a move with little to no drawbacks when used with perfect accuracy- like other moves, namely Focus Blast, Blizzard, and Thunder, it was designed to be an extremely powerful STAB moves for those pokemon who get access to it with just a 70% accuracy, which gives it a drawback. Much of Pokemon works because of opportunity costs- the opportunity cost of using powerful moves is almost always inherent, such as in moves like Close Combat, V-Create and Superpower. Most extremely powerful moves (namely those above 100 BP) have a secondary effect to balance out their ridiculous damage output and possible secondary effects (see Inferno, Zap Cannon as well) and this drawback is what makes the moves not widespread and easy to use. Pidgeot takes a move that was designed much like this extremely powerful moves- Hurricane- and throws its drawbacks out the window. No Guard Hurricane is frankly ridiculous because it's a 110 BP STAB with absolutely no drawback, which is a point I have seen less discussion on than I would like to see. In fact, not only does it have no drawback since it will hit 10/10 times instead of 7/10 times but those 3 extra times that it hits will also give it a chance to confuse the opponent, leaving walls completely at mercy to luck, in some stages of the game. However, that's a point I'd like to give my opinion on in the next paragraph. While No Guard Hurricane, in my opinion, is what makes Pidgeotite so inherently broken, Pidgeot leaves a lot to be desired power-wise; its meager Special Attack (135 is nothing for a Mega without the ability to hold an item; Mega Alakazam stayed around for a while because its damage output frankly wasn't that great and standard defensive pokemon could beat it, despite it having 170 SpA) leaves a lot to be desired and the same can be said for its coverage moves and movepool. While undervalued when talking about Pidgeotite, Pidgeot's notable movepool includes the aforementioned Hurricane, and also Heat Wave, Roost, Work Up, U-Turn, Defog, and Protect (which almost every Pokemon gets access to.) It also has access to Tailwind, I suppose, but that would most likely be a waste of a moveslot for an offensive pokemon and the only reason I include Defog despite my dislike for Defog Mega Pidgeot and opinion that it's a waste of a moveslot on such an aggressively offensive Pokemon is because Defog is few and far between in every tier, especially UU. That movepool leaves a lot to be desired and doesn't give Mega Pidgeot a whole lot to work with, and really only gives it two sets; on one end, it can kind-of-beat the pokemon that could "switch into" it with Heat Wave but Heat Wave isn't even that great of an option when clicking Hurricane will almost always be better and Doublade already takes almost 40% from Hurricane, for example. The other set is obviously the Work Up + Roost + Refresh set which still relies on getting near-perfect paralysis rolls on Blissey to win, since it has to somehow boost on a Blissey that spams Thunder Wave and Soft-Boiled while being constantly pressured by Seismic Toss.
I'm going to shortly focus on its effectiveness vs each playstyle, and hopefully this helps to explain Pidgeot's inherent brokenness. Offense is perhaps the best off versus Pidgeot, because like it has been said above Offense doesn't need a switchin for Pidgeot, and as long as offense does what it does best and gets up rocks immediately and pressures Pidgeot with stuff like Ice Shard Mamoswine and CB Tyrantrum it's usually going to be perfectly fine. Not having a switchin for Pidgeot isn't even realistically a problem because it's offense, and having a switchin for every threat goes against offense's very philosophy. Balance is in a different boat and has a lot of issues vs the Work Up + Hurricane set (doesn't even need Refresh in this instance) and not as many vs the Hurricane + Heat Wave set although it can have problems depending on confusion rolls. First of all, every balance team is going to run Empoleon- this is understandable, even in a Pidgeot-less metagame. Empoleon is a great answer to Flying spam in general and is a great SR + Defogger which is something you won't find in any other Pokemon in the tier. Pidgeot just polarizes Empoleon to the top of usage on balance, because otherwise balance is going to have to run more shaky but still incredibly solid answers, like Mega Aerodactyl and defensive Rotom-H. Both of these are great pokemon outside of checking Pidgeot and checking Pidgeot is just another one of their redeeming qualities; however, both of these pokemon are worn down by rocks and Mega Aerodactyl has a 15% chance to lose if it switches into Hurricane, while Rotom has no reliable recovery unlike Aerodactyl and risks being 2HKO'd if rocks stay up and it doesn't immediately Pain Split when Pidgeot switches out, since Hurricane is still doing about 25% the first switchin, leaving Rotom at about half its HP, and when Rotom switches in again it is easily 2HKO'd after rocks if it isn't above about 75%. However, that doesn't stop Rotom from checking Pidgeot on balance, since it can easily switch in once and do a massive amount with Volt Switch, leaving Pidgeot in revenge-killing range for any Pokemon that outspeeds it. Florges is a decent answer but automatically loses to the Work Up set because it doesn't even do half with Moonblast, and if the 15% chance of confusion occurs it will always lose. This means that Pidgeot has absolutely no reason if Florges comes in on Hurricane than to click it again, because Florges will always click Wish and Pidgeot then gives itself even a higher chance of getting a Hurricane confusion and ending Pidgeot's life. Balance also will always run some type of revenge killer or offensive Pokemon that can always live a Hurricane- this inclues pokemon like Mega Aerodactyl, Mega Beedrill, and Scarf Mienshao, as well as pokemon like Heliolisk, Tyrantrum and Salamence. However, said slower Pokemon always have a chance to lose to the unavoidable in any argument about Pidgeot- the 30% confusion chance on Hurricane, which turns into a 15% when you consider the 50% chance included to hurt themselves in confusion. This means that slower pokemon like Salamence have a 15% chance to be confused by said Hurricane and hurt themselves and therefore lose the matchup. Stall is the final point in this paragraph, and the ideas about stall have been all over the place in this thread, with people saying things like Pidgeot is ineffective versus the stall archetype to things like Pidgeot easily 6-0s the stall archetype. In my opinion, Pidgeot is somewhere in the middle- Work Up / Refresh / Roost / Hurricane is obviously the set to dwell on here, since all other sets just lose immediately to Blissey. It's important to note that not every Pidgeot will be this set- in fact, plenty will lack Refresh or Work Up or both since they want to do more work to offense and don't feel the need to give up 2 coverage moves or utility moves if their teammates already handle stall well enough. The only way that Work Up Refresh Pidgeot beats blissey, actually, is through rather insane paralysis rolls- Pidgeot has to dodge being fully paralyzed a number of times in a row to sufficiently boost vs Blissey, all the while spamming roost practically every other turn (if not every turn if it's being fully paralyzed sufficiently enough) because Seismic Toss is doing about 30% every hit which does wear down on Pidgeot's own health. Realistically, the scenario of Blissey vs. Pidgeot can never be accurately portrayed because it's completely luck-based; if Blissey goes for Thunder Wave as Pidgeot goes for Work Up, assuming both are at 100%, if Blissey ever gets 3 full paras in a row Pidgeot is as good as dead. Realistically Pidgeot has to work its way through a lot of full para chances to realistically beat Blissey, but stall also can run pokemon like SpDef Taunt Roost Toxic Aerodactyl (which is a great set) and physically defensive RestTalk Ampharos to check it alongside Blissey. I definitely think stall has the largest issue because of this particular set, but it has ways to deal with Pidgeot like every other archetype. However, there's still one last part of Pidgeot that I have yet to talk about in this long essay-like post so I'm going to write one more paragraph and hopefully that should cover all of my thoughts.
This is the final paragraph of my argument, and focuses on the confusion chance of Hurricane, mostly whether or not this confusion chance should be regarded as legitimate regarding Pidgeot's banworthy aspects. This is the part of Pidgeot that I've been dwelling on since Pidgeot's suspect test has been brought up, and I've never really found a tried-and-true answer to whether or not Pidgeot's confusion chance should be truly considered when tiering Pidgeot. On one hand, Smogon typically tries to avoid needless luck-based aspects of Pokemon, which is why moves like Swagger and abilities like Moody have been banned in the past. Hurricane confusions can't be related in the slightest to those moves, and once again like Mazz said above Scald is much more broken than Hurricane, because it's more widespread and dangerous in the tier. I don't think the Hurricane confusion chance is reason enough to ban Pidgeot- the 70% chance of the Hurricane confusion not occurring can't be nonchalantly passed up when making an argument, because the majority of the time when using Hurricane, statistically, a confusion will not occur and a safe switch-in will come in, pokemon like Rotom-Heat, Aerodactyl, Mega Ampharos, Snorlax, and Empoleon, and they will be able to do what they do best and wall Pidgeot. CurseLax can setup on Pidgeot, Empoleon sets up and defogs away hazards, Ampharos and Rotom threaten it with Volt Switch, and Aerodactyl threatens it with Stone Edge and can use the opportunity to pull off a roost or even a Hone Claws. However, the Hurricane chance cannot be underestimated, because a 30% chance is much larger than it seems. That's the same chance as a Body Slam paralysis by Snorlax or a Scald burn by Suicune, and each of those pokemon get a fair share of secondary effects with the given moves in any given game. The confusion is enough to completely neutralize some would-be checks, as well- Empoleon doesn't really care since it won't even take half from Hurricane + Confusion + Self-Hit + Hurricane, but Snorlax risks being 3HKO'd with a confusion, Florges just dies to a confusion, Rotom-H if it's defensive risks being 3HKO'd with rocks up, Aerodactyl dies but most Pidgeot users won't risk that, and Mega Ampharos is worn down so easily that chip damage is just undeniably rewarding for the Pidgeot user. The 30% confusion chance cannot be understated, but despite all of this, I still don't believe it's the main reason to ban Mega Pidgeot, it's just the reason that Mega Pidgeot is over the top. Pidgeot doesn't lose anything from clicking Hurricane, like any other 100+ BP move; instead, it gains something by getting to use it for free and having that 30% chance to near-neutralize a defensive pokemon. And this is why I believe Pidgeot should be banned as my opinion stands right now- because a limit on teambuilding due to incredibly limited switchins, a great speed tier, access to a set that can do extraordinarily well versus stall, offense, and balance at the same time all combining together with a 30% chance to confuse Pidgeot's next switchin just pushes Pidgeot way over the top. It has switchins, albeit limited, and those switchins are going to do what they do despite taking damage from Pidgeot (I'm mostly talking Empoleon and CurseLax here since they are the two best switchins to Pidgeot, in my opinion) but it's not like Pidgeot doesn't have teammates to deal with these Pokemon, and Pidgeot always has a chance to confuse these Pokemon and leave them even weaker until the next encounter. Its positive aspects greatly outweigh its negative aspects and polarize the tier around it to a certain point which is not optimal.
I'm sorry for the length so i'm going to leave a tl;dr here: Pidgeot's speed, access to No Guard Hurricane, and great matchup versus every playstyle in the tier along with its confusion chance are all incredibly good positive aspects which greatly outweigh its bad points, and its switchins are so few and far between that a simple 2 or 3 pokemon core surrounding it will cover almost everything that it cannot stop on its own, and then some. The confusion chance of hurricane pushes it above just a stellar wallbreaker, and turns it into a polarizing machine of a bird which I wholeheartedly believe is banworthy.
