@ext: It is Youtube.

I use other adblockers (including Opera's built-in adblocker), and still lags a lot.
(I mean, a pc with a RTX2060 shouldn't even sweat a drop with YT, and it does freeze a lot)

People complaining about Youtube being slow with this add-on:

This is not only from ABP. I use Opera's built-in adblocker, and stil YT lags. It has to be the website.

I can confirm it too. It is happening to me with both my home laptop and work's PC.

Laptop specs: I7-8750H, 16GB DDR4 @2666mhz, RTX2060M 6GB.
PC specs: I5-10500T, 16GB DDR4 @2666mhz, Intel UHD 630.

Both in the latest version (107.0.5045.15), updated every 2 weeks.