Ark: Survival Evolved: Low fps becaue of UE4 or due to no optimizations?

No i’m not saying that at all. That would be totally wrong. There is nothing wrong with using blueprints or 3rd party plugins - those are great features of the engine. You are misinterpreting this.

I’m simply saying that the game was released with executables compiled in debug mode, linked to pdbs which are exposing the whole projects source-code so everyone can see that it’s mainly made out of blueprints and that the project is based on the ShooterGame example by Unreal. This is not incorrect, is it ?