Those Megas being soft-balled balance-wise do sound like an overcorrection “new” Pokémon-wise after what happened in Scarlet and Violet’s infamous power creep. Annihilape and Gholdengo’s signature moves being nerfed, and Archaludon no longer having access to Body Press, are at least more sensible fo make them more bearable to fight against.
Too bad Sneasler, Kingambit and Basculegion run rampant with no serious nerf.
Speaking of those three, Annihilape and Archaludon, there’s something so impactful of having a brand-new evolution that find success in VGC given that anyone can run more than a single cross-gen evolution, unlike Megas where you can only activate one per team, even if using more than one Mega Stone; one per team in general or one at a time in Z-A.
As for my opinion in Megas in general, I used to be cool with them given I believed we won’t see new cross-gen evos ever again except Sylveon back in Gen 6, but between the very severe imbalance between them, how much popularity is too determined even for Pokémon that don’t need such a big boost, and the fact that the one-per-team is even more limiting the more new Megas we get, I feel like it’s something I can live without, and won’t mind seeing it rebooted or revamped in a fangame or two.

As for my changed opinion that occured within a year? Archaludon, the new evolution of Duraludon introduced in Scarlet and Violet. I am very shocked to see a Pokémon with 535 BST to evolve, though having better Abilities in Sturdy and Stamina for Archaludon helped soften the blow, but otherwise I wonder how could Game Freak handle the stats with only +15 BST (onto 550 like Ursaluna and Kingambit)…
Needless to say, Archaludon revealing to having 600 BST akin to Pseudo-Legendary Pokénon, despite being a cross-gen evolution (or perhaps, because of) have greatly won my favor due to several factors, one of them is that it is more in-line with how Duraludon is envisioned as a rival of Tyranitar by having matching BST, alongside Archaludon’s improved bulk, Stamina and Rain-boosted Electro Shot combatting Tyranitar’s high Attack and Sand Stream which comes with a SpD boost on it.
Helps that while Duraludon is built up as a VGC starring species with redirection-ignoring Stalwart and a Gigantamax form that ended up flundered due to various factors (i.e. Special Defense of 50 way too low for it’s 85 Speed), Archaludon managed to find a solid success in VGC with Rain team, or even with the help of Sableye or Grimmsnarl. Even the absence of Assault Vest in Champions (as of this writing) and Body Press being removed from it didn’t stopped Archaludon to be a serious threat you will have to respect in it’s presence.
Speaking as someone who was extremely hyped for Duraludon when it was revealed, I do agree that Archuldon felt like the perfect (almost necessary upgrade) that Duraludon needed to hang around some of its psuedo rivals.
Duraludon I think was dealt an unfortunate hand. Given that it was the first non-legendary Steel Dragon Type, I feel like Gamefreak went overboard to ensuring it was balanced by giving it a bunch of handicaps. Its stats (specifically its offenses) were well tuned, but they saddled it with 3 useless abilities, very unfortunately distributed bulk, and an extremely limited movepool that didn't leave it with many options. I imagine the goal was to make Duraludon a bulky utility Pokemon similar to Tyranitar or Landorus-T, but in practice that didn't quite pan out, even with its amazing 535 BST. 70 / 115 / 50 bulk just wound up feeling frail in practice - like shockingly frail, to the point where neutral special attackers from weak defensive Pokemon like Clefable were dealing over 80%. Not helping matters was how Duraludon's Steel / Dragon typing made it neutral to types you would want a Steel or Dragon to resist (such as Fairy and Ice for Steel & Fire for Dragon) giving it less oppurtunities to pivot in compared to some of its peers. 70 / 115 physical bulk wasn't bad, but given Duraludon's weakness / neutrality to common physical moves like Earthquak or CC, it too didn't feel like enough on that side either. These factors sort of funneled it into running an Assault Vest to patch up this issue, which is fine, but it couldn't run those cool utility moves like Stealth Rock, Iron Defense or Thunder Wave, which was unfortunate. In a vaccum, I wouldn't mind 95 points of stats going into attack - after all a lot of my favorite Pokemon like Tyranitar were so fun to use precisely because of their versatile stat spreads letting them dip into their special movepool for Coverage. However, Duraludon also didn't get any strong, worthwhile moves on the physical side - Swords Dance was cool, but you would be running that with 2 weak 80 BP STABs and weak 75 BP Coverage making it hardly worthwhile. Interestingly, Duraludon could still function as a mixed attacker of sorts with Body Press being its best move to hit Steels, so it made these points spent in attack feel quite wasted. On that note, its special coverage was also a bit lacking as well. Dark Pulse and Thunderbolt were actually pretty great moves it had access to, but it didn't get much of anything for Steels and Grounds, leaving it feel easily walled.
Overall, Duraludon felt like it was quite handicapped from reaching its full potential. When Archaludon was revealed, I was hoping that they would refrain from jacking up its offenses too much and focus on shoring up its key weaknesses - namely its movepool, useless abilities, and rather low defenses. And sure enough, they did exactly that.
From the moment it was revealed, it was shown having two new abilities - Sturdy and Stamina - that were significantly more useful that any ability Duraludon had. Stamina was definitely the main prize - working great with Body Press to help against some of its normal counters- but Sturdy was also a great new ability to let Archaludon function as a lead Stealth Rock setter while being able to hold another item like Power Herb, Custap Berry, or White Herb.
The stat increases I think were also perfect. It would up getting incredibly modest gains in offenses - only 5 to Special Attack and 10 to its (largely) useless Attack stat, with its speed remaining unchanged. Its biggest gain was to its bulk. Its hard to describe, but 90 / 130 / 65 - while still leaving it frail on the special side - is such an enormous net gain to its special bulk in practice. Case in point:
0 SpA Life Orb Clefable Moonblast vs. 0 HP / 0 SpD Duraludon: 220-261 (78.2 - 92.8%) -- guaranteed 2HKO
0 SpA Life Orb Clefable Moonblast vs. 0 HP / 0 SpD Archaludon: 181-214 (56.3 - 66.6%) -- guaranteed 2HKO
Yeah, you still get 2HKO'd in the above example, but you reduced the damage overall by roughly 30%., letting our Dragon Friend better function as a trade Pokemon. the physical bulk is also astronomical now, and further amped up by stamina, letting Arch take a super effective attack in a pinch too on that side + powering up its Body Press. All of these traits add up to let it actually better leverage those cool support moves it had access to like Stealth Rock, Dragon Tail, Body Press, etc. to better act as a bulky ultility Pokemon.
Its movepool also expanded in the right way IMO. Aura Sphere gave it some good special Fighting Coverage for Steels (in case it didn't want to use Body Press for whatever reason), it got an actually good Ground-type move in EQ on the physical side which it can whip out for Clodsire or for funny SD Sets (which are also just better now because of its better defenses), it randomly gets Focus Energy now which is fun in its own way to remove Draco Meteor's Drawback + its better able to leverage this thanks to its newfound bulk. Randomly gets metoer beam for some funny shenanigans. And this is all without mentioning its new signature move - Electroshot - giving it a one of a kind niche on rain teams. On that note, making Archaludon a rain Pokemon was such a creative and interesting direction to take it in general. Most Rain Pokemon have typically just been Water-types that spam big water moves with big speed, so making a non-Water-type Pokemon like Arch into a rain threat (which as a steel type synergizes well into rain because of its Grass / Electric resistances + Dragon / Electric offense into Water Resist) was just such a cool concept that they nailed.
If I did have one issue with Archaludon's design though - it mainly is just Electro Shot because it lets it snowball a bit too fast. I think the main issue for me is that Electro Shot gives a Special Attack Boost before it fires, so even if you counterplay this by switching into a ground-type, you get nuked by a +1 Draco Meteor. I think I would change this so that the Special Attack raise occurs after the shot Fires, making it easier to switch into and play around. I don't really like how this has become Arch's identity either. I think its mixed attacking niche with Body Press was really cool, but that has effectively been gutted with it losing that move in Champions (though they thankfully didn't take away Aura Sphere).
One other cool thing about Arch is that - in SV at least - its existence also makes Duraludon better at its role since it can now hold Eviolite, letting it be the bulky Garchomp / Lando-T / Ttar type of utility Pokemon it always wanted to be. It still gets the big special defense boosts from Eviolite, which makes it genuinely bulky on both sides & it can still slot in those cool utility moves it gets. Though, a con in post champions games is that it now loses Body Press so it can't fulfill any mixed attacker shenanigans or hit opposing steel-types too well.
Errr yeah, my b for hijacking this thread, but I just wanted to gush about Arch since it completely redeemed duraludon from being a disappointing.
As for changed Pokemon opinions - I initially did not like Leon's Champion theme since it was just a remix of the Hall of Fame theme. However, after listening to it more over time, its grown on me pretty heavily. Its a bit melancholy - like the end of an era sort of theme, if that makes sense.