So, I did my best to follow the arguments here, but I had a lot of trouble following, I think in part due to a lot of weird false reasoning used on both sides. Because of that, I'm going to kind of go back to the beginning on this one.
Lileep's role in the metagame is as a wall (this isn't really disputable). Therefore it should be compared to other Pokemon based on what it can check and counter, how reliably it does it, whether anything else can check and counter what it can better, and how common the pokemon it checks and counters are. Then, we should examine its role in the greater metagame.
What it beats:
The list of Pokemon you provided that Lileep checks is "Chinchou, Staryu, Tirtouga, Spritzee, Porygon, Foongus, Cottonee, Abra, Carvanha, Ponyta, Archen, Drilbur and Snubbull". Of these, I would say Lileep counters all
Chinchou, Foongus, Carvanha, Ponyta, Drilbur, and Archen sets. I would also add Vullaby to this list. Life Orb Staryu beats Lileep, SS Tirtouga can just set up until it wins if rocks aren't intact, Spritzee clicks Calm Mind a bunch of times and gives no cares, Cottonee can lock Lileep into a recovery move with Encore and stall it out, Life Orb Abra has a pretty decent chance at winning, and Close Combat Snubbull reliably 2HKOs.
What does this better:
The short answer is, there is a Pokemon that checks each subset of those Pokemon that has greater viability than Lileep. Snivy and Foongus check Drilbur and Chinchou (and sort of Carvanha), and have offensive presence and Spore, respectively. Ferroseed checks every Pokemon on the list except Ponyta (and some weird Foongus variations), and can stack spikes. Chinchou beats Chinchou (ban this please) and Ponyta, and is an excellent pivot. The key thing to note, here, is that
every one of these Pokemon can check a subset of what Lileep can without losing momentum. And this is the recurring theme of this post, and the reason that Lileep should stay exactly where it is: in an offensive metagame, most teams cannot take the momentum loss that Lileep creates at the expense of defensively checking some Pokemon that could be checked without losing momentum. However, I do concede that Lileep might be the only way to counter that list of Pokemon that reliably. This gives it a niche, and is the reason Lileep is ranked at all.
Lileep in the Metagame:
Lileep suffers from 3 major problems in the metagame:
1) As I discussed in the previous point, Lileep is a huge momentum killer. Unless it is up against a Water-type or weak Flying-type, Lileep's way to kill Pokemon is usually click Toxic and then click Recover a lot of times. In a metagame built around strong setup sweepers and powerful wallbreakers, this is not sufficient. Although Lileep does possess decent offensive stats for a defensive Pokemon, it can't really abuse them with Giga Drain and Ancient Power (unless you get that 10%). And yes,
I know Lileep can use Curse to boost, but it doesn't give Lileep enough of a boost to keep up with setup sweepers boosting alongside it.
2) Lileep is Fighting-type bait. You conceded this point above, but you don't seem to understand the ramifications. As long as Pawniard remains in this metagame, Fighting-type Pokemon will be the absolute defining force in the metagame. Giving a free switch-in to Mienfoo and Timburr, at least one of which is on practically every well-built team in the metagame, is certainly not something that can be passed over lightly. It's not just that Lileep is weak to the Fighting-type either: its that it really just can't do anything to stop them from coming in, except poison them, or deal practically nothing with Giga Drain.
3) Lileep is dead weight when it isn't killing momentum. Basically, if Lileep isn't coming in on something which it specifically checks, it becomes dead weight. Knock Off significantly inhibits Lileep's ability to function, and it has to be wary of coming in on one (even from Pokemon it does check, like Vullaby and Archen). Most offensive Pokemon that aren't on the checks list above can simply muscle past Lileep, which is not a good thing for a defensive Pokemon. Also, many team types punish a player for using a Pokemon as passive as Lileep, such as VoltTurn, heavy offense, and really anything built around a setup sweeper not named Zigzagoon. Essentially, if Lileep is not losing momentum by doing what its supposed to do, its doing nothing at all.
I'm not saying Lileep has no qualities, and I'm not saying it has absolutely no place in the metagame. I am, however, saying that its negative qualities outshine its positive qualities enough that a bump in the rankings does not seem warranted. Also, for the future
Fille, we generally only nominate a Pokemon to move up a place or two at a time, not all the way from the Cs to B+.