"POM seems to be faster than throwing more polygons" Good to know but I did heard the contrary from some people in the gaming industry but I never tested it my self and this was years ago, so things most have changed by now.
But even so even if POM is faster and look awesome when it works, there's no denying that it has serious issues with curve surfaces and characters.
And your totally right about UE5 nanite, IMO this focus on that tech, is creating huge performance issues for modern games, some developers are even stopping making custom LOD's anymore and relying entirely on nanite.
And is not only nanite, mesh shaders are gaining popularity and they gave rise to D3D12 "meshlets", that is what Alan Wake 2 uses for example. The Remedy engine debug visualization of them, does look very similar to that of nanite, so perhaps they are the same thing?
Lumen is another thing that IMO is creating big performance issues and ugly noisy games, even TAA cannot solve that, I played a indie UE5 demo of a horror game and when I entered dark rooms and turned on the light, it took almost half a second for the light to resolve, it was very jarring.