That God is necessarily beyond human conception is an explicit teaching of my religion, the Baha’i Faith. I suspect it’s probably at least implicit in every religion, and may be explicit in at least some of them. The idea that God is constrained by our conceptions of Him is more a position held by those who don’t comprehend religion than the religious. At the same time, it does help to have some kind of conception to hold onto, even if we acknowledge that it is necessarily incomplete. We just have to be careful to make that distinction. It’s rather like science, actually, in which we build models to describe reality, but we must always remember that the model is not the reality.