none of of these things solve anything.
not in the here and now at least. if you have infinite GPU power... maybe...
at this point, in most games, using any of these is often a sign of devs just pressing a button to get easy results to the detriment of performance.
Nanite is only even remotely good if you use extremely high polygon counts. and even then you can often get better performance by not using Nanite. Nanite is a shortcut for devs that allows them to not needing to do proper LODs.
!!!UPDATED MEGA THREAD!!! This post has been updated to include every major performance test against LODs posted through the current 142 post included here. There is no need for mindless scrolling over opinions and arguments for the facts. Note, these tests get progressively more complex and...
forums.unrealengine.com
Lumen often looks like absolute shit, especially software lumen, which has a blotchy and unstable look in indirect lighting conditions nearly 100% of the time. while Software Lumen reflections look like absolute crap as well, heavily relying on Screen Space Reflection overlays, and therefore defeating the reason to use RT in the first place.
and games like Silent Hill 2, which have nearly 100% static lighting, should never even think about using Lumen GI, yet they do, due to the aforementioned easy shortcut it is compared to manually adjusting lighting and baking the GI.
and Megalights still has to proof itself.
Unreal Engine 5 often leads to devs using quick and fast solutions that run worse, instead of proper optimisation to run well and look exactly as good or even better than using Nanite or Lumen.
while this isn't UE5's fault, it is clearly influencing developers to go down that path, because it's simply easier and therefore cheaper.