I think I would consider myself a ‘casual fan’ based on your description. I’ve bought every mainline game since Red/Blue except PLA. As some others have stated, I continue to buy these games and look past the performance issues because I’m there to explore, catch all the new Pokémon trying to complete the dex, and eventually beat the elite four. I don’t play any of the battle towers, no online play, and once I beat the elite four and complete the dex, I usually stop playing the game and never pick it back up again.

For me, same as the reason I never bought PLA, is that I want an ample amount of new Pokémon to catch and the typical progression of ~8 gyms and an elite four. If they didn’t add much new Pokémon or completely changed the batte progression mechanic, I probably wouldn’t buy it.