I don't understand how people can say that. If you honestly believe that's true, then you've just nullified the whole foundational purpose of religion and deemed it false. Either the religion preaches the word of God, and is therefore moral by default, or it does not preach the word of God, and is therefore immoral by default.Religion doesn't have to be absolute and unchanging, you might choose to call that selling out but there's no reason why religion cannot or should not adapt. It's almost funny in some ways that if religion tries to adapt then it gets slated for it as selling out, if it doesn't then it's an anachronism - seems there's no way to win.
If religion adapts as time goes on, then it's quite clear that there's nothing holy, nor supernatural about it (which should be apparent anyway).