The issue is Crytek knows what to do to make things run better and faster, it can be “tricks” and not necessarily some regular optimization step that’s known everywhere (just guessing). Because for example, if UE4 has every optimization like other engines, Cryengine is still capable of handling like hundreds of dynamic lights in a single level like in crysis 3, while UE4 needs only 4 dynamic lights to lose half the games frame rate.
Cryengine got there because it didn’t have any static lighting solution, so they had to make it work fast with dynamic lighting otherwise Crysis series wouldn’t exist. But since UE4 has lightmass and Epic never tries to create something realistic in large scale, they never try to improve dynamic lighting as their projects can go on with static lighting. Main improvement Epic does to dynamic lighting is to say “Don’t use dynamic lights here and there”.