It's a bold move, I'll give them that. I'm happy to see Game Freak has the balls to mix things up again, to me Gen 4 felt to similar to everything else. The fact that they have balls to make changes is what im more interested about.
My gripe though is the national dex usually doesn't come into play until after the region champion is defeated. It seems redundant to collect 493 pokemon that only serve to fill in the dex. If they make enough content post - region champion like traveling to another region (old or new) and have another main quest to follow, then it'll be all worth it.
So whether or not it's a good decision really rests with how much content we get post- pokemon league. Otherwise I'm going to have to agree with haters and call "filler".