Everytime Firefox updates I have to restart the entire browser or it won't let me open a new tab. This has been going on for years. As a dev, I can't dynamically edit source during runtime ever since the Quantum update. It's noticeably slower these days, which is especialy bad on mobile/laptops due to battery life. If you're on Windows, you don't get video super sampling (NVIDIA) or HDR videos.
I wouldn't call it a buggy mess that crashes frequently, but it's certainly constantly getting on my nerves.
Except premium pays the people that make the content. ReVanced is, regardless of if you hate big tech, blatantly stealing the work of the skilled artists you enjoy.