The same thing could be said about UE4 versus UE3, or UE3 versus UE2, or UE2 versus UE1. But that's because updates and improvements are incremental. People just dunk on UE5 because this is the first time a major version has dropped since it became available to indie-level developers, and a ton of indie devs are doing an abysmal job of assessing and understanding the fact that a major version means breaking changes that need to be properly accounted for. The more committed your project already is to an existing engine, the worse the update will hit you.
Also, sweeping generalizations about performance and visual changes are, well. Sweeping generalizations. That isn't to say you're wrong in the case of Breeders of the Nephelym. Derelict has demonstrated either an inability or an unwillingness to actually utilize the optimization potential in UE4, so upgrading to UE5 with that attitude will probably make things far worse. A properly optimized UE5 game will, like a properly optimized UE4 game, run just fine on far more machines than people on this forum would assume.