I understand how this works with something like fire, everyone can agree that it is hot. How does this work for the concept of God?
Well stated, yet within that statement is a metaphysical/epistemological conundrum. The modern problem is entirely focused on the concept of God as opposed to the reality of God.
St. Thomas Aquinas said that the immutability of God is His strength. God never changes, although man in his finiteness seems capable of only recognizing and emphasizing only a part of God at a time. The failure of some to recognize Him for who He revealed Himself to be, does not alter His real existence or nature, for lack of a better word. That the earth is round is an objective fact and ought to be a universal truth, yet there are flat-earthers even today.