The older I get the more I'm realizing that the basic flaw in religion is two fold. The unprovable and the unknown.
1) Any religion based on any book puts full trust in that book as truly being 'Inspired' and not just any man's or group of men's musings and assorted conclusions and selected narratives. They therefore claim to have a 'divine commission'..a claim which is unprovable.
2) Any/all religion has as it's basis earthly origins or ideology. It uses fear of the unknown to exercise control.
ie unless 'a God/Higher Power' actually physically speaks to the world it all comes down to belief/trust in men and a belief that only one religion is the 'true religion', when really no religion is the true one....
religion is therefore inherently divisive and a breeding ground for extremism. unless a divine power ( if it exists at all!) intervenes, religions are able to build up a constructed historical basis and a future based on transient ideology. Basically religion is deceptive. It claims to be authentic when there is no tangible method to prove authenticity. 'Religion being the opium of the masses' increasingly rings true.
Please excuse my rambling....!