I'm on a 13900K with an RX 6600 and it is barely usable for me as well. Firefox tho... just tested in Chrome and it is better after the initial scroll but that first move is a killer.
Yeah, Firefox on my office desktop (10-core i9 with 16GB RAM. Crap GPU though) was unresponsive for a good 30 seconds before I was able to close the tab. Worried for a sec that I'd have to force close the browser.