Considering the quality of YouTube's Apple TV app[1], this should come as no surprise, and frankly it's probably for the best. This type of thing is better off starting small with applications that actually work well, instead of bolting on some well-known names that are just going to phone it in and disappoint users in the long run.

[1] Anecdotal, but: it recently added its own screensaver that plays instead of the system one, and never stops playing, meaning if I accidentally leave YouTube open, my TV never switches off. The VLC app can't discover UPNP services on my network as long as YouTube is in the recent apps list. It decides to be in French sometimes. (Our system language is not French). And, not entirely Google's fault, but there are about three different ways to cast a YouTube video from the iOS YouTube app to the same gorramn TV, and which one is actually going to work today is completely random.

The indifference YouTube gets away with on Apple TV tells me, if that team made an app for Vision Pro, it would provide guaranteed headaches. Apple is dodging a bullet here.