I usually try avoid religious debates on HN though.
And sure, I get your overall point. I was Christian until age 26. I worked two years as a missionary in a foreign country, 90hr weeks, no pay, for my Christian beliefs. What "God" meant to everyone I encountered throughout that time, before, and after, is/was always a bit different. Ultimately we create our own personal God, and what that means can be compatible with honest and rigorous scientific inquiry. But you have to throw out large portions of the bible and accept that it's largely a work of art and useful fiction, and I will place $1000 down on a bet that the vast majority of "Christians" would bristle at such ideas.
But yeah, best to stay away from discussions of religion with anyone except your closest friends. Even then it's usually ill advised unless you have hours to sift through the nuance and are very good communicators.
"Believe" is absolutely the right word; most of us don't have the time, inclination, or ability to perform the scientific method required to demonstrate evolution, big bang, or old earth. Outside of a very small number of people, the overwhelming majority of us are taking it on faith that these theories are correct.