I don't like Pokémon Legends Arceus that much. The open areas feel empty and the lack of trainer battles made me bored. I also don't like the battle system either. More often than not you either get totaled in one attack or the opponent spams moves while you struggle to catch up. The inclusion of a more in depth Pokedex completion system is nice. The problem is it can make actually completing an entry feel like it takes forever. Of course a part of these feelings comes from the general burn out I feel toward open world games. I'm genuinely concerned I won't enjoy Scarlet and Violet because of the genre alone.
I also felt PLA to be very underwhelming. I absolutely HATED the battle system and I pray that it never comes back. I honestly think that the classic pokemon battle system is one of, if not THE best of any turn-based RPG. Instead of using this battle system and ramping up the difficulty of the battles, we get this FF-X-like battle system that does not work for Pokemon (FF-X's battle system works great for that game, but not in PLA). Taking away the ability to switch if you have a slower pokemon with a type disadvantage removes a classic strategy that has been a staple of the franchise since day one.
I also found the core gameplay loop of catching pokemon to get pretty dull and boring (granted, catching pokemon is one of my least favorite parts of pokemon games and I will usually use 6-10 mons in my non-nuzlocke playthroughs). The story was abysmal, which is an achievement considering how bad most stories in this franchise are. I also was disappointed on how they handled the lore of this game. For a game called Pokemon Legends Arceus, it hardly expands on the lore of this mysterious diety. If anything, Palkia and Dialga got more new lore than Arceus did (albeit as a result of the single worst design in the series in Origin Dialga).
I did love how easy it is to change movesets of pokemon. I'm glad that the previous few generations have given the player many options to learn great movesets, and PLA's changes to learning moves make this even better. I also liked how you could catch pokemon without battling them.
PLA was a (kinda?) ambitious pokemon game, but I feel that many of the changes made were either half-baked at best, or genuinely awful.