I’ve worked with UE4 professionally for several years - this is absolutely true. It’s hard to get really good performance out of the engine. Furthermore, it’s a beast. The codebase is large and old enough that making deep modifications is very difficult and time consuming.
That said, the tools are (mostly) great.
Absolutely NOT! UE4 has great tools and awesome APIs for creating content from the perspective of an artist. The runtime, unfortunately, is mired with legacy code from a bygone era. It is also restricted by the need to maintain mobile support. Compared to an engine like what idTech has, or Activision, or Ubisoft, etc. the UE4 runtime is probably 10 years behind. There are numerous techniques such as those mentioned in the linked post that are simply not possible in UE4 because of how dated the RHI layer is.