John Carmack was already at a reduced role and it appears that much of his advice which was mostly about what they should optimize was not being made a priority. Optimization got VR to the point of usability but it is unclear if it's still the most critical path.

Although Carmack had a few ideas he always said he didn't know what the right direction to take was. So I don't think his value was that critical, particularly with his reduced role other then for hiring. Also they still have Michael Abrash.