We still don't have fully hardware accelerated video playback in browsers under Linux. To check this, watch a 4K video in the browser and look at the CPU usage.

Edit: I can block ads in various ways (pi.hole, etc.) but I can't fix laggy UI. I'm always using Linux on one of my PCs so that I can follow how it's progressing, but Win10+WSL2+VcXsrv gives me the best of all worlds.