In my O P I N I O N the pokemon get better as the gens get later but I hear the games get worse

I've played FireRed, Emerald, Shield, and HeatGold so far, planning on Plat next. And while they're good games (except shield), the availability kills me in all of them (except shield). I wind up with two or three pokemon I like and the rest are just filler.

Gen 5 and onward have tons that I like, so the challenge isn't finding enough to fill out a team moreso as deciding who gets benched. But it seems like the actual gameplay gets worse. (I really didn't like Shield minus the availability.)

Does anyone else feel this way?