Again, Zuck's success criteria don't necessarily align with that of others. In fact, I'd expect his success criteria are substantially different to most.
This has not been my experience. I've an Nvidia desktop and AMD HTPC, both running Wayland and a wide variety of games. What's more, they both do variable sync and HDR.
This and machines with 5090s are a completely different market.
The Steam Machine is marketed primarily as something sitting under your TV. I don't have 5090 under my TV money, 99.9% of people don't. That's not the target demographic.