The Add-On is not designed for Android or mobile browsers. The mobile version of YouTube uses a different website structure and player, which makes it technically impossible (at least with my current knowledge) to provide the same features, such as changing the audio track for example.
And by the way, the Add-On never claimed to support Android or mobile browsers. When an add-on does, it's clearly mentioned on its Mozilla Add-ons page. So it's a bit unfair to complain about that.