Great Add on - it removes all the annoying parts of Youtube and creates a distraction free clean look.
It is customiseable, you can select what you want removed. It even offers Darkmode for its menu - I love it! Some bad reviews are just because people are unable to click on the extension and select the option sliders they want - it is that easy.
By default the playlist sidebar is hidden, I recommend turning that of!
I think the extension is essentiel and happily donated a whole 4 $