(I’m not asking agnostics or atheists.)
Anyone who authors any such claims are merely fallible human beings, right? E.g. Mohammed only said he spoke with the angel Gabriele. Come on, is it not arrogant, or just plain foolish to claim to know anything about God, based only on what human beings wrote, without first having a personal, face-to-face conversation with God about at least a few verses and chapters in scripture? Much less every verse, chapter, and book available.
Mere human beings wrote them all, and the version of scripture that people adopt is inevitably chosen mainly on the basis of whatever their local culture believes they should adopt. No first-hand proof needed, just the comfort of being accepted by society or by special friends, or in some cases, just the self-assuring confidence that one knows truths that other non-believers do not.
No circular reasoning allowed here, like the Bible is true because the Bible says says blah blah…