I agree with the gist of what you're saying, but having used ue4 for the last 6 months on a side project and not having any real art skills, I've found that the particle effects editor is a fantastic way to mask my own art deficiencies, and secondly having a fully featured lighting system out of the box gives me another very good head start. I'm still stuck for texturing, modelling and animation, but having a powerful engine does give you a leg up.