You haven't though, not really.
Quest needs a PC to play the games, or a subscription service to a streaming platform.
This will play them natively, with no internet, and no PC.
Edit: I mean how the hell are you going to just "magically" play sprite based games like Vampire Survivor in VR automatically? If that's not UE, that's not the point, there's no way for a user-friendly, non-vomit inducing way to just flip ever game to VR.
At BEST you have a simulated 3DTV where you get a 3DS-like effect on the flat games so there's depth to them, but they aren't VR.