Honestly, Unreal Engine isn't the greatest engine when it comes to performance, but I also get the sense that publishers know it's going to be used as an excuse to let them off the hook, when the real issue is that developers are overutilized in an industry of low employment due to mass layoffs.
I have been developing a pretty large (1900 sq.km) small-grain (so not Minecraft-like) voxel world (not really a game at this point) in UE5 and there are plenty of resources available to make a performant experience. Often improving performance is a matter of just writing proper game-code (in C++ or Blueprint, it doesn't matter.)
My large world isn't close to being done and is still asset sparse, but getting it to be traversable on an RTX 4060 laptop (roughly 9th Generation console performance, if not slightly weaker) at 1600p 60fps wasn't hard to do. I have lumen and nanite at appropriate levels and was even considering moving to a non-lumen ray-tracing implementation. And again this is a voxel world using voxel plugin that has a lot of rivers and water with heavy use of semi-realistic fluid dynamics with Fluid Flux.
Who knows, maybe once I start adding a lot more assets this will bog down the performance.
Of course my "world" is mostly CPU-bound at this point (and uses a lot of system ram), but I see no reason why a well-staffed team couldn't optimize games with UE5. It's really just an anti-worker industry giving us poor titles at this point, in my opinion and blaming the game engine is an easy out.