It complicates things in the context of adding an 'entity' to the equation without any additional explanatory power. Consequently the first cause argument is no more explanatory than assuming the universe itself is its own cause (e.g. it self-exists without anything additional beyond it).
I guess I see what you are getting at. I'm not sure I agree, though. To me it, because it does answer at least that if he is the origin, many things can be reasonably extrapolated from there that necessarily preclude many other encumbrances --at least, that is concerning absolute origin.
I think it does give some explanatory power; I cannot accept a God who is less than First Cause. And since God, is necessarily as First Cause above all, and all powerful, and all things were made by him, I can also begin to see that he makes according to his nature, and for his own sake, and many other things begin to make sense, including sin.
If by "explanatory power" you are referring to the physical / mathematical provable ways how he did what he did, I think we would have to go a lot further with our cosmology. So maybe you are right there, yet I keep hearing hints --eg. people like to say quantum particles appear from nowhere, uncaused --really? Also, long believed laws like conservation of energy, and logical laws like non-contradiction and so on, at least to me, point to both his nature and the necessary fact that those very laws --indeed logic and existence itself, are his "inventions", which he did not suddenly himself pop into being subjected to. They may seem to be simply "what is" or "the way of things" but that has, to my mind at least, be his arrangement. Not simply fact.