While I mostly agree that the hardware and UX challenges are mostly out of his domain,
> It requires engineers to ship high FPS and low lag to prevent nausea to a degree unheard of for PC gaming.
This is very much Carmack's speciality, and why his focus was on making mobile VR happen [0]. There are very few people who can outperform him at that, and most of them worked for Oculus :-)
[0]: https://www.gamedeveloper.com/design/q-a-carmack-reveals-the... (this predates the Quest, but it should give you an idea of the problems he was tackling)