I want to address two things.
While I do agree that some of the Megas like Houndoom, Altaria, and Banette could have ( and probably would be better off ) as cross-gens, I want to address two issues:
1. Ace Pokemon getting Megas. Yes, Megas also exist to promote merchandise, which is the reason why Charizard and Mewtwo got two, and Pokemon like Garchomp and Gengar got one. Remember, Pokemon is a merchandise driven franchise, so people who did not play Pokemon for long time will se their favorite Pokemon getting Megas and want to play the game. At least Megas were not soley Gen 1 unlike Alola Forms and Gigantamax.
2. The biggest issue I have is the subjective nature of how a Pokemon's stats correlate to its role. If that was the case, Articuno would be in the same tier as Zapdos, or Typhlosion as Charizard. People say Salamence should not get a Mega Evolution due to being a Psuedo-Legendary, but Goodra is also a Psuedo-Legendary and its in NU. Metagross is also another case of a Pokemon who people argue should not have gotten a Mega, but its in RU as of now. And that’s only looking a Smogon tiers. Dragonite gets significantly less usage than Goodra in VGC, does Dragonite deserve a Mega over Goodra in that case?
And that goes back to another topic I want to discuss: Difficulty. Before I go into this, I want to bring up other observations. I’ve been hanging on Fire Emblem Forums recently, and I have often noticed a huge series of complaints against Fire Emblem: Three Houses, with some people saying it’s the worst series; here are some of the complaints: “ The Monastery is a chore “, “ The Minigames are pointless “, “ Maps are too simple “, and the “ difficulty is too easy “. Don’t those complaints sound familiar? Anyway, I think it’s a shame that people feel that way about the monastery and minigames, because I really do believe that they really fit in the world of Three Houses very well and helps brings out it themes; in other words, Three Houses is a game that rewards you for taking the time to learn about your peers and participating in activities with them. People who just wanna go from battle to battle with little to no break are not going to enjoy the game because that’s not how it was supposed to be played.
But enough about that. I want to talk about the Map Design particular. Fire Emblem has a rough history especially in the west. The first five games were never localized in the west, and when they did start localizing them, they did not sell well. A big factor is how difficult the older games were. Not only did they feature huge maps with multiple objectives as well as being a huge time sink, Fire Emblem was famous for permadeath, or when Charcters die, they are permanently removed from the game. This made the games notoriously difficult, which is probably why when they started localizing the games in the west, they struggled to be super popular: The learning curve being too difficult really made it hard for newcomers to be invested. There wasn’t any option to turn off permadeath until New Mystery of the Emblem, which was the 11th game in the series. Radiant Dawn was widely criticized for being too difficult by western critics, and difficulty settings were mistranslated in English: Hard is Lunatic, Normal is Hard. Ever since Awakening, which saved the franchise form cancellation, the maps become a lot simpler in design with more simple objectives like “Defeat the Boss” instead of “Seize”. The developers noted the complaints and tried to appease both veteran players and casual players with Fates, with the Conquest Campaign being designed to be a challenge with complex map objectives and limited resources, while Birthright features simple maps and allowed grinding making it ideal for beginners. Despite that, they went back to simpler maps and objectives in Three Houses. Why? Simply put, most people or Casual players don’t like, or don’t have the patience to handle super complex maps the older titles. Fire Emblem was almost canceled, and they don’t want that to ever happen again. That’s why the newer games have been designed with a casual approach in mind, they want someone who started with Three Houses to stick until the end of the game- they do not want them to quit just because the game was too difficult.
Newcomers will likely have some difficulties with Three Houses. I know that for a fact because I am a veteran and gave a copy of Three Houses to my brother, and he had some pretty hard times in the game. Even I had found Three Houses difficult at some points, and I am a veteran player.
So what does this have to do with Pokémon? Well, all the logic I’ve used in the paragraphs above applies here. Just because a small minority of people find the game easy, doesn’t mean others will. For someone playing XY as a veteran might find it easy and find Megas overkill, but for a newcomer Megas might just be what makes the game passable after being too difficult. I’ve played XY several times, and in one particular run I actually struggled against Olympia because her Meowstic set up too many Calm Minds and I did not have a dark type. I actually lost, and yes, as a veteran player, I lost in XY. How tragic!
In conclusion, when looking at design choices like difficulty, it’s more important to consider casual or one time players, people who only play game once. Those are the people who vastly outnumber those who do Ironman runs as well as those who play the same games multiple times. While I can echo some people express disappointment that Pokémon games have become streamlined recently, I can understand why they do it from a business perspective and the fact that most hardcore players who do things like nuzlockes are in a minority and do not weigh much in comparison to the casual/newcomers.
Catching up, if any of y'all wonder why I'm liking posts from 2 months ago, that's why lol.
I simply must comment on this though.
The biggest issue with Three Houses might very well be the map design, similarly to how Pokémon's difficulty issue isn't necessarily tied to difficulty.
Basically, a lot of modern FE maps are very, very cool to look at, and Three Houses does have some remarkable battles, like the big battle between the three houses in Part 1.
The thing is, how often do you need to approach things in a different way in that game? I'm hardly one to talk here, I treat all maps like a Rout Enemy map, but the lack of distinct strategy requirements makes the game rather lackluster. Many maps are vast open fields with some forests and thickets and you don't really get defensive maps with Ballistae or anything more interesting geographically-wise. Edelgard's paralogue being the closest to it.
The problem people point out the most in Radiant Dawn was that the Dawn Brigade was essentially a team comprised of a bunch of Magikarp-like units against pretty buff enemies. (No DB slander tho) It was like picking BW1 mons and sticking them in Platinum. In comparison, Three Houses units are extremely flexible and grow into forces of nature. Naturally, that's going to make things more difficult, but some paralogues will still get you if you think the game is free.
What does all of that have to do with Pokémon?
Now that you have so many options to make obscenely strong teams, the difficulty issues are glaring, but that doesn't mean you go full hackrom-mode and crank up that level curve.
A much simpler solution, much like how Three Houses should've tried to spice up the maps a bit for the same reason, would be making some effort to have major battles be unique. How? Strategy.
Take Viola in XY for example. Not quite the hardest boss in the franchise, but she's far more interesting than say, Bugsy having a Metapod and a Kakuna for... reasons. Why is that? Because she at least tried to run a non-RNG-reliant gimmick.
Similarly, SwSh could've used a bit of flavor with their gym leaders. For example, Milo has a Gossifleur, and an Eldegoss. One of the biggest issues with that battle is that it's incredibly easy to pick a bird, like say, Corvisquire, D-Max on turn 1 and fold him like an omelette without him being able to do much about it.
Now, both of these mons have a unique ability that inexplicably isn't used in that battle, Cotton Down.
The biggest criticism with in-game D-Max is how it's so easy to get a sweep going with it, but when you're constantly losing Speed just for attacking, that opens you up for Milo to counterattack. Granted, I don't see Magical Leaf helping a lot here, but Grass mons have a lot of annoying options, including another disruptive option that also doubles as a speed control tool. Stun Spore.
You don't need to make the leaders hard, you need to make them
interesting. Most pokémon bosses are really solved with "Pick type advantage. Mash A. Same as routes. Cool music optional." This example is a bit too stall-oriented, so what about we try a more offensive battle?
Look no further than Mustard. He already leads with a Mienfoo with U-Turn, right? Why not play up on it and give his Shinx Volt Switch?
On the post-game version, (Yes, there are two separate trainer entries, why he'd have an Lv. 61 Shinx is anyone's guess, but Klara/Avery can't even claim sandbagging or trolling on that, which is even more embarrassing.) Mustard could upgrade these to a Regenerator Mienshao with U-Turn and an Intimidate Volt Switch Luxray, giving them much better synergy. (This is post-game, so it's fine to take off the kiddie gloves a bit.)
Are these harder battles? Yes, because quite frankly, SwSh was too easy even counting the kid target audience. But they're not overwhelming like say, HGSS Lance, Plat Fantina, GSC Miltank, Colosseum Evice, and that tier of straight-up raw, buff mons trying to fold you with brute-force.
TL;DR - The difficulty issue is not that Pokémon is easy, the problem is that it's boring. Add thematic strategies as gimmicks.