I think this tends to be an unpopular thought in the anglosphere Pokémon fandom but I am glad they bother having actual plots in the mainline games. Because otherwise you are playing a slate so blank they may as well be transparent. The player characters genuinely have no identity beyond their designs. As someone who does not self insert into stories the way others do, I need the person I am controlling to have SOMETHING. I do not feel the need to make my own story in a mainline Pokémon game because the protagonist barely exists beyond eye candy. Also, some of the regions are just uninteresting, but that's a different tangent.
I mean, Pokémon Masters EX basically has to make up characters for the protagonists. And like Red only started being an icon or something after being in GSC where we could, I guess, get some hints of him being reclusive? overly dedicated? Whatever makes one climb the top of a mountain and not contact your Mom. It's a fucking joke how the Sun Moon protagonists have a blank smile throughout the entire game. The fact your character emotes in Legends Arceus is revolutionary.
TBH a lot of monster tamers have this issue. You play as Nothing that you're supposed to put yourself into. I feel a disconnect about it, from these games and their fanbases. Uhm... I still like some of them for having interesting bits of worldbuilding, at least. Like Hoenn, Sinnoh, Unova, Alola, they have fun worlds to me. I like what Palworld says about its monsters, and the kind of culture that's formed on the Palpagos Isles. Coromon's plot is, interesting, at least before this rewrite the devs didn't elaborate on. Or there are games that are just fun enough that I can bypass this issue, like Moonstone Island, Monster Rancher 1&2, or maybe Abomination (although this is a bit different as you don't play as one character but rather a rotating group that shifts based on your playthrough and who survives). Telefang 1 is a mix of both of these; having a silly/engaging enough plot/characters/world and game mechanics that make it stand out a little more.
But also some games actually give the character you're playing as, conviction, a "purpose" so to speak. The Dragon Quest Monsters games come to mind. Particularly the last one where you play as the final boss of DQ4, Psaro, and see him grow in power and prestige in the monster world, and I think even change the timeline eventually. Uh, I lost all my progress on that game before I finished it unfortunately. Or there is also Nexomon Extinction which also gives your character a certain backstory that builds on the world and relationships established in the last game. It also characterizes the MC as a weirdo, because the writer is silly.
I can imagine that everything I'm saying is probably alien to other people and, I am not purposefully trying to be contrarian, these are my feelings from my heart put into words to the best of my ability. Please tell me your thoughts too on the way protagonists are utilized in monster tamers, I want to understand you too.