Youtube has been hiding videos from me for years. I’d look at my “Subscriptions” page, and wouldn’t see anything new. Then I’d go to the channel’s page, and see a few new videos.
That prompted me to start using my RSS reader instead of youtube subscriptions. A more reliable experience, for sure.
I’m OK with it existing, but it should be an addon. Not something that Mozilla pushes onto people who don’t want it.
Silicon Valley has a consent problem, and Mozilla is no different.