I don't think Apple wants you to use Mac apps. They want developers to make Vision Pro apps. That's why the Mac integration is the minimum they could get away with.
There are enough devs that love Apple and have a burning loyalty toward them, that this is not something I would worry about. Even if it started to become a problem, Apple has enough cash to make a lot of apps, and could subsidize this for an eternity if necessary to make it work. Apps will not be a problem.
Do you think Netflix and Spotify are really needed (genuinely wondering)? Netflix maybe because of exclusives, but I would think most people with Vision Pro are also going to have Apple Music. With their TV and Music offerings, it might actually be better not to have Netflix/Spotify etc.
How do you know? Where do you get the numbers? Vision Pro isn't even out yet so I'm curious how you could know this. Do you have inside-Apple insight? Such as how many of the people who ordered Vision Pro are on Spotify vs Apple Music?
Hope they are not really betting on that, think it's clear to everyone that OS fatigue hit when they had 3 OSes and lots of companies stopped bothering after that didn't pan out as worth it now this would make 6 OSes...