I don't learn from other religions. They're so far out in left field that I don't see any value in them.
What happens is I get inspired to examine Christian teachings more closely when unbelievers, atheists, and people of false or errant religions criticize Christianity. I have learned a lot from that. It's valuable because they are honest. When something doesn't line up in Christianity they are honest enough to confront it and point it out. But most Christians, it seems, will toe their denomination's line no matter how contradictory or wrong even they have to admit they are as if they are somehow doing the right thing for God by doing that.
It seems many Christians think it's a sin to question what the church teaches. But we can learn so much if we would dare question what teachers are teaching in the church, we just need to do that with the right attitude--not to rationalize going back to our old lives, but wanting to genuinely know the truth.