> And Valve not supporting Mac again shows that relying on outside industry is not a viable strategy if you are not the dominant platform. Mac wasn't a big platform for them to sell VR titles as it's not used by many consumers to play VR titles, so they drop support.

Yes and no - I think part of that was also that Apple is openly hostile to other app stores on the Mac. It's true that third parties are lukewarm in their support for Mac, but it's very hard to disentangle to what extent that's the effect of Apple's lukewarm support for third parties rather than the cause of it.