Does adding self-serve onboarding actually lower your conversion rate?

We automated our entire onboarding process to let users jump straight into the app without talking to anyone. But our conversion rates plummeted because user got confused by complex settings and gave up before seeing the core value. It made me realize that removing friction sometimes removes the guidance people actually need to succeed.

How do you strike the right balance between a fully self-serve signup flow and high-touch human onboarding?