Performance problem with this extension after few years, low FPS on youtube/twitch and other video platform, because this extension just recalcule CSS and reinject itself too many time per minutes, this issue is present for several months now (9 or 10 month).
Please, do something, something less aggressive in your code if you found a video in the page or a thing like that...

Every time I want to watch a video smoothly, I have to deactivate this extension.
Screen with Youtube video in 4k for example : https://i.imgur.com/h4gVGqi.png (3 extension active, Roboform, ublock origin and Dark reader on a fresh firefox 92.0)

my PC spec : RTX 3080, Ryzen 5900x, 64go Ram, All on 3 SSD Gen 4