Having similar issues with my 6900 XT. Destiny 2 is the only game it happens in. IMO don’t expect a fix from Bungie because I’ve dealing with it for quite some time now. I’m on Windows 10 so it’s not happening just because you’re on Windows 11.
Yeah it was happening when I was on Windows 10 as well, and performance didn't change when I upgraded to Windows 11. I was also having suboptimal performance on my previous 5700xt ever since Beyond Light. For a while the game was totally unplayable on up to date drivers, but even after Bungie "fixed" that, performance wasn't actually GOOD.
It seems like Bungie just doesn't support AMD cards, and doesn't seem to care about supporting them. I noticed not a single streamer I can find uses an AMD card, and I bet it's for this reason. Bungie should either begin to properly support AMD or advertise openly that they do not.
I have a 2nd PC in my home with a 3080 Ti and these issues do not exist on that system. I also came from a 5700 XT with similar issues in this game. Bungie clearly either plays favorites or the developers incapable of optimizing their engine for modern GPU architectures. I’ve seen some post on Reddit from people with 30 series cards saying that they also had issues in Destiny 2. It seems like there’s a decent amount of people claiming that performance in this game has been very broken since Beyond Light came out.