If you can beat YouTube's DRM then you can just make your own player app. No need for root.
If you can't then what makes you think you could defeat whatever checking for rooted devices YouTube would add to their app?
Anyway, this sort of discussion is pretty pointless. The market has spoken. The number of people who care about root access is tiny compared to the number of people who want a safe device and app experience. Heck the entire iPad/iOS experience is pretty much "let's take a general purpose computer, make it do less, and it'll sell much better".
Works fantastically.
[1] https://f-droid.org/repository/browse/?fdfilter=NewPipe&fdid...
After that you are allowed to install .apk files (e.g. clicking the "download of xy.apk finished" notification or in a file explorer app).
Edit: that setting is always there, it's only greyed out if you installed a corporate app that explicitly disables it (e.g. the "GoodApp" email/calendar/contacts suite).
EDIT to match your edit: you remember wrong, the option is always there (unless there is some manufacturer out there that blocks it (Amazon maybe?), but most devices certainly don't)
Oh yes, this. I pay for Google Music which is supposed to include that, but I do now have it by virtue of living on the wrong side of some border.