I will say that I actually hit a HUGE plateau in Plat 2 as well so I totally feel where you're coming from here. I spent like an entire month there myself before I finally started to get back on the rise, it was rough!

Specific to Street Fighter 6, the two things that I think helped me get past that level were actually pretty non-character specific. The first was getting consistent at counter-DIs and also feeling more free about throwing out DIs in things that look like they could be gaps in the offence. The second was just getting down exactly one really good cheap block punish I could do consistently. I usually do about an hour of training mode once a day so it was easy to throw these into my drills and get the inputs consistent, but honestly, getting the DI reactions down really came from just being able to do dozens of sets against the same friends who were willing to ruthlessly exploit that reaction weakness until I finally closed the gap.

Past that, more generally for fighting games, the best bit of advice I've ever gotten for getting past plateaus was from @pattheflip: watch your replays and take notes on them. It's tough because it's kind of annoying and it's definitely work. But it also makes your weak points really obvious in a way that's a harder to analyze when you're distracted by actually playing! I'm actually about to start doing that again myself, since Diamond players are scary as hell and I've noticed that a lot of my bullshit doesn't work anymore.