Yes, this may be true; but you also may be wearing some nostalgia glasses.
Everything about Pokémon (and many Nintendo games, but with many exceptions) is designed to be accessible. That's one reason Nintendo/Pokémon is so popular. Every game has catered to new players in some way, and fan service in the series is sort of limited.
Think about it - the games have never been very difficult. The mechanics have never been very complex. The game never misses a tutorial. The Pokémon games are aimed at younger audiences, and as the current audience ages and becomes more critical, inevitably we will cease to experience new games the same way we used to.
That being said: I'm wearing the same glasses as you. In my opinion, Pokémon peaked in generation IV. Diamond, Pearl, and Platinum (and (HG&SS) featured the perfect roster of Pokémon, a near perfect difficulty curve, a relatively mature storyline and plenty of content, but that's my opinion and nothing more.
In some ways, the quality of the games has gone down. We haven't had a really good battle frontier in a bit, and many players dislike certain changes like the in-battle type effectiveness checker or whatever you want to call it. (but again, that's just to help new players)
Inevitably, we, the players, will grow up. We become more critical of what we play as time goes on - after all, life is short. And to that end, we may have left Pokémon behind. In the end, Pokémon hasn't changed all that much, but maybe you have.