When you think about it, it's kinda obvious why those games are getting worse and worse. Look at the history of game development in general, games nowadays require much more time and a bigger work force to deliver next-gen experience. Development cycles were about 2 or 3 years back in the 2000s, now it's 4 or 5, or even longer.

Now think about Pokemon, which is basically a yearly release, sometimes 2 years. Expectations are getting bigger since it's in 3D already yet we are seeing a genuine drop in quality in all aspects. There's also the aspect of GameFreak being tired as fuck with the brand in general, they have been making those games for over 20 years now.

In conclusion you can't expect good Pokemon games anymore simply because it is literally impossible with their development cycles and limited staff. As for business practices like cutting monsters from the dex, that is purely a business decision made to cut corners and gain bigger profits from cutting said corners. Again, it's literally, factually impossible to get a good Pokemon again in this day and age. You would need to have more experienced people and at least 3 years for a Pokemon game to come close to being good. As long as there are yearly releases, you will never see anything good again. The older generations required less time and effort to be put together so it was possible back then, it is not now. I can't think of any developer in the world releasing good games every year without having multiple large teams of developers.

Do you genuinely think Pearl/Diamond remakes will be good? Think again