I'd argue that that's orthogonal; this is making the general UI work well on a TV, then apps get populated into that. And honestly I'll bet that for most uses Firefox working well is what you want, since a handful of shortcuts to open Firefox to assorted streaming services would do the trick quite nicely.

I immediately envisioned having my feed reader as a FireFox shortcut and being able to navigate to YouTube videos from that.

Another thing is that I've found certain old movies can only be streamed from weird websites - as in https://weirdstreamingwebsite is the only licensed entity to have it. I could either buy a VHS (which is what we did) or stream it. But since a physical copy might not be available, the only option would be to use that weird website to stream it. There is no app!