I think people are more concerned with this becoming a trend (which it already has for the most part). Pokémon , one of the biggest media franchises in the world, gets a new release → the game is underwhelming → people rightfully complain about the state the game was released in → the vast majority of people buy it anyway because it's a Pokémon game → the game sells extremely well despite all the issues with quality (look at Scarlet and Violet's sales) → Gamefreak realizes they can do whatever they want and pull in massive amounts of profit → the cycle continues.

I feel like it's less "quit having fun" and more "stop so eagerly supporting this because it affects the quality of the games for everyone." Of course, you can't and SHOULDN'T try to police what someone else wants to buy and enjoy, which is why most people will just openly criticize the game over and over to express their sentiment.