“None of these guys (Abraham, David, Moses, Jacob, etc.) would receive ministry credentials today!”
We have a God who gives a lot more than just second chances; your fallenness, your sin, your wounds, your track-record - it doesn’t rob you of fruitfulness. These were men who met with God outside of "church", outside of formalised religion, outside of any "role" they had taken on in life. They did not filter their spirituality or relationship with God through their ministry assignment - they met Him mano e mano ... well, mano e God-o anyway... Because they didn't have to keep their reputations clean, they could face their failures and shortcomings squarely and openly when God confronted them. They were concerned about God's attitude to their sin rather than the opinion of other "leaders" (e.g. "Against You and You only have I sinned" - David in Psalm 51).
Having been a pastor, I feel so sorry for many of my brothers and sisters who have reputations to protect, images to uphold. And often neither is of their own choosing, it's a construct of the congregation or denomination.
The "successful" mega-church pastors, the perfectly-dressed and supposedly incorruptible televangelists, the ones whose churches dub "the Lord's Anointed" - I'm afraid I don't relate. Give me an irrational Simon Peter, a lustful King David, a bad-tempered Moses, a sneaky Jacob any day - each is a man who is real enough to authentically encounter God and show me the way to do the same...