It’s not just that God is powerful and capricious. I think all gods are portrayed that way. It’s the promise of infinite punishment for finite sins that is special to Christianity.
And back when most people lived in small, culturally homogenous communities, and didn’t know much about the world outside their community, you could at least say, “we all know what God wants of us”. But today that’s manifestly false. Each community has a different idea of what God wants us to do. Many of those wants are incompatible. And there’s really no good way to determine who is “right”. Surely, if God really wanted us to behave in certain ways, God could have been more clear in communicating that to all of humanity.
So either God wants different people to do different things, or God doesn’t actually care all that much, or God is intentionally setting up most of humanity to rot in hell. (Or there is an underlying flaw in our understanding of God, such as believing in such an entity at all.)