The features are palatably fine, but the UI, the design are unintuitive and not cared meticulously.

in 4:3 Videos there is no volume control.
eg:
https://www.youtube.com/watch?v=w_NEIf8-d9c

It will sometimes make "YouTube Livestreams Theater Mode" stopping to show chat on top of the video.

줄거운색상으로 감상할수있어 참조아요..

Since the latest update, the options to hide comments and chat stopped working. All the other options make immediate changes like before, but those two options don't do anything anymore.

The Pop Up player doesn't work with the latest version.

YouTube Videos Opening Time slowing this extension.

Reasonable features, but reversing a playlist makes the player pop out into another window and there's no way to make that not happen. I uninstalled it since that was the only reason I downloaded this extension in the first place and I don't want pop-up windows. Ever.

Automatic quality selection simply doesn't work.

Amazing usually but lately ad block doesn't quite work.

On FIREFOX ONLY! Volume control with the mouse wheel is just random :( Instead of following the wheel, the colume level just keeps rising for about 30 levels when wheel is moved up and vice verca for down. In effect volume control with mouse wheel is completely useless.
THe same feature works fully on my Brave browser with the Chrome extension

all these features and still no subtitles

why does mozilla and its extention devs not care about accessibility for people with hearing or attention issues

Update suggestion: I wish i was able to load the full content of the video without rebuffering, as i see some extentions on chrome does that.

Je suis un peu déçu, car il manque une fonction bien utile qui permet d'activé la traduction des sous-titres lorsqu'elle ne sont pas dans la langue par défaut du navigateur

The addon does what it claims, however, at some point it started to have a huge problem - it only works once. If a load the YT page, and then it dets discarded, on subsequent view the addon never activates on it, no matter what I do. I can reload the page or even de-activate and re-activate the addon - it doesn't help, it won't load on the same address ever again.

Also tried rolling back to a much earlier version - while this problem seems to not happen as much, then addon stops blocking ads, which is an equally bad problem...