YouTube vanced was a pretty awesome modded version of the regular YouTube app, except it basically had all the traditional YouTube premium features (like adblock, background playback etc...).
But it also had some awesome extras, such as Return YouTube Dislike and SponsorBlock support...
HTML5 is a lag fest on older architecture and comparing HTML5 to Flash during video run-time is like comparing beans to eggs. Flash is superior and actually RUNS where as HTML5 crawls.
You can actually easily restore the flash player without any extensions and i wish i knew this simple AF...