The "if you complain about the game then don't play it" argument is flawed.
We complain about new pokemon/new features because we are passionate about pokemon. Most people who complain about the new pokemon are original fans of 1st and 2nd generation. To me, and a lot of people, with each generation, pokemon gets worse. To us new pokemon simply aren't as interesting/lovable. It's natural that we're going to complain, we want things to be different. This doesn't mean that we HATE the new games or new pokemon.
It's interesting that the subject of first-person shooters came up with this. With FPS games so many people use the "if you complain about the game then don't play it" argument. If you look at halo, people complain about the most minute things in the game and then those people get flamed to hell, told to stop playing the game if they hate it so much. The thing is, the people who complain most about the game are actually the people who love it most, they want the game to be perfect. Bungie (for those, who don't know develop halo) listen to their fan's criticisms. And consider the fanbase's opinion when designing weapons/maps, that's why they released public betas for halo 3 and halo reach. They WANT criticism, that is why they release betas of the games (as well as for marketing reasons, of course).
The same thing sort of applies to pokemon, but to a lesser extent. I love pokemon, and I know that pokemon, for me anyway, apart from nostalgic reasons will never be as good as it was with the first two generations. This won't stop me from complaining. I love pokemon with a simple design, as do a lot of fans. If we complain about how pokemon nowadays aren't simple enough, the designers have to at least take into account this fact.