Engines like Godot and O3DE and other FOSS game engines need their own version of Nanite.

I think the lighting will once and for all converge on Raytracing eventually once it becomes mature hardware-wise (and most GI schemes are basically it, but watered-down voxel-based versions already, including Unreal's Lumen), but virtualised geometry is also a HUGE deal. Like, you can 3d-scan an object and just chuck it into the game, no manual retopology required, the virtualized geometry algorithm will take care of it.

It reduces effort greatly, and makes development rapid. Which is why people are able to make those wonderful scenes even before the engine was officially released.

Yes, that means the models are huge in raw data. But it also means they can always be optimized later if the need be. The interesting part - creating the actual game - comes first.