What a random, entirely unpredicted, but completely necessary nerf.
Substitute as a move was incredibly powerful in its own right. While I didn't read much in the way of calls for it to be nerfed as a move, it was warranted to a degree. I hated Sub Kyu-B, Sub TKon, Sub Gyara, Sub Garchomp, all of these bulky offensive 'Mons that could run Substitute and had access to so much power through two moves at least that in certain cases, they could bypass set-up moves and just destroy teams regardless. I never anticipated a nerf but I'm somewhat glad one does exist.
This nerf was excellently done, though. The fact that it's just sound move users and Infiltrators that get it is excellent. Neither set is exceedingly distributed and gives Pokemon with access to one or the other a new niche they previously didn't have, giving them opportunities to fill a role they otherwise wouldn't possess or, in some cases like Crobat, help that Pokemon excel at what it already does. Overall, substitute is still an exceptionally powerful move that, when used correctly, makes your reading game a hell of a lot smoother for you, but there is now more counterplay than there was before.
I do think that this means you'll see Crobat and possibly Chandelure in OU as a result, as they now gain niches as stallbreakers but I don't see much else changing. Sound moves won't really be used for the sake of bypassing subs as, in certain cases, you sacrifice some to a decent amount of power to use them over a better move. It's simply just a nice change for the Pokemon that did use Bug Buzz or would use Boomburst that they wouldn't otherwise get.