Unreal engine

Imagine if it ran like utter shit like UE4. Like ARK or PUBG?

UE4 does not have "the graphics", that is a result of how the games are designed. It uses prebaked lighting of rather awful quality and some rather antiquated and bloated shader systems. What riot currently uses looks better than the same assets would shoehorned into UE4. All it would do is lock out most of the playerbase (who use Intel iGPUs) from ever playing again, give some nice shadow artifaction, and ensure nobody ever gets 200 fps again.

What exactly do you expect from it?