Just my opinion, I think at least a portion of them have to learn to live with "faith" being the answer to some hard questions. You also don't have to look hard for doctrines that are contradictory. For example: was Jesus human or God? (and keep in mind that God is traditinally viewed as tri-omni, meaning omnipotent, omniscient, and omnibenevolent)
Many times I've asked that I'm told "he was 100% human and also 100% God." I'm sure different sects believe differently on that, but plenty do accept that. When I ask "how is it possible to be 100% human and 100% God?" you'll sometimes get answers like, "well it's like water in different forms, ice, liquid, and vapor" but that doesn't answer the question (it answers a question about how Jesus and God the Father can both be God yet still be "monotheistic"). When pushed it has always come down to "some things have to be accepted on faith." That is obviously enough for plenty of people, but I personally find it insufficient. Back when I was a believer I had cognitive dissonance over that question that I somewhat learned to live with (obviously not entirely as I am no longer a believer, but it wasn't that question that led me to ultimately lose my faith).
Many times I've asked that I'm told "he was 100% human and also 100% God." I'm sure different sects believe differently on that, but plenty do accept that. When I ask "how is it possible to be 100% human and 100% God?" you'll sometimes get answers like, "well it's like water in different forms, ice, liquid, and vapor" but that doesn't answer the question (it answers a question about how Jesus and God the Father can both be God yet still be "monotheistic"). When pushed it has always come down to "some things have to be accepted on faith." That is obviously enough for plenty of people, but I personally find it insufficient. Back when I was a believer I had cognitive dissonance over that question that I somewhat learned to live with (obviously not entirely as I am no longer a believer, but it wasn't that question that led me to ultimately lose my faith).