Mega Sableye got it's prankster nerf and the changes to mega evolution made it so it can't Will o Wisp and evolve at the same time, which give it a kick in the teeth.
Added some more viable Fighting types (some of which got banned) that can deal with Chansey easier, Thunder Wave nerf, basically it became easier to handle
Clefable got to face more steel and poison types and more stallbreakers which kicked it in UU for a short period of time.
Skarmory got to face one more important Electirc type, Tapu Koko and more special attackers which again, made it easier to handle

It looks like SM OU is more balanced than ORAS OU now that the Bravest Bird is gone.
Until you get to see Dugtrio being able to patch up it's crappy attack that previously held it back(with those stupid Z moves), now being even better at removing setup sweepers that could threaten the stall teams.
If that wasn't enough, some GENIUS at Gamefreak created the piece of shit in pic related, buffing this stupid and broken playstyle at idiotic levels and now it's even worse that it was before.

T-thank you G-gamefreak...

>inb4 git gud