Look at the outcome of Meta's performance in AR/VR over the past few years: a fortune has been spent; relatively little has been achieved; the whole thing is likely about to be slashed back; VR, something Carmack believes in, remains a bit commercially marginal and easily dismissed; and Carmack's own reputation has taken a hit from association with it all. You can understand perfectly well why he doesn't feel that it would have been harmless to just let other people have whatever fun they wanted with the AR/VR Zuckbucks.

(Mind you, Carmack himself was responsible for Oculus' Scheme-based VRScript exploratory-programming environment, another Meta-funded passion project that didn't end up going far. It surely didn't cost remotely as much as XROS though.)

It's insane how VR has succeeded beyond most people's wildest dreams on the hardware front (all that hardware that goes into a VR headset either sounded like science fiction or seemed like would be exotic stuff costing tens of thousands of dollars), and the software also had standout successes, but it kinda just petered out both in the entertainment and professional realms.