I'm gonna say something else people hate to hear:
Third Strike is overrated. I love the game, but people suck it off way too hard as the "greatest 2D fighter of all time". That's a highly subjective claim and I think there are other 2D fighters that do certain things better than it (RBFF Special and KOF '97 - '98 with backgrounds, for example)
About SF6 though, there is something I will agree with: tho I do like a few of the character themes (Chun's, Kimberly's for example), overall the OST is simply not my flavor. It's mostly like some modern trap/drill hip-hop and I think almost all of that sucks. Given SF6 is after SF3 timeline-wise (seems like) and SF3 took place between '97 - '00, then I take it SF6 takes place probably somewhere in the mid '00s to mid-late '00s time-wise going by Li-Fen's age.
So I would've liked at least some hip-hop more era-appropriate to the timeline. But some variety never hurt, either; 3rd Strike had hip-hop, house, jungle, DnB, and a decent number of those with clear motifs mixed in like funk, rock, blues etc. SF6's soundtrack doesn't seem to have any of that type of variety, and while there are some motifs in some of the songs, they're very light and minimalistic. I'd also say while SFV's OST wasn't the series's strongest, it has some standouts, like Zeku's and Karin's themes, that are way above any song in SF6 from what I've heard so far. Those two themes are legit classics among all-time SF themes, can't say the same for anything from SF6.