Try installing URLCheck (it's on F-Droid) and make it your default browser, then remove open-by-defaults from the YouTube app.
It should let you open in the ReVanced or better yet Morphe version of YouTube. If tapping the link doesn't open URLCheck, then "Share" the link and select URLCheck.
Ah, I wasn't aware, thanks. That's unfortunate, they really did improve the UI (at least since I last tried ReVanced)