I haven't played Sun/Moon but X/Y had just as many features as Black/White if not more. They streamlined breeding, and EV training. They added in Mega forms to shake up the meta. They stopped adding 150 poorly thought out Poke'mon and instead focused on giving us about 70 well thought out additions. They made the jump from 2D to 3D.
Now, I agree with OP that the main story mode has gotten more linear. And I agree that it is a problem.
There’s no poorly thought out Pokémon in BW
Trubbish, Garbidor, Gothita, Gothorita, Gothitelle, Lilliepup, Herdier, Stoutland, Ducklett, Swanna, Foongus, Amoongus, Alomomola, Boufalant, Stunfisk, Pidove, Tranquil, Unfeasant.
Not to mention they went completely overboard with the legendaries. There's like 12 of them in Black/White.
Don't get me wrong though, Black/White was an awesome game with some very strong designs. It just also happened to have quite a bit of filler pokemon sitting aside the well designed ones.
I liked X/Y for giving us 71 new Poke'mon and 30 new megas. Do I think there are some bad designs in X/Y? For sure. But there aren't as numerous as previous games in the series.