That’s really the worst feature of it. When you first set it up you’re asked at least a dozen questions that you probably have no idea what they mean. But you have to pick something. And whatever you pick on that first day setup you are stuck with FOREVER. Unless you do a complex data migration task.
Also, want to migrate to a different provider? Sorry. You can’t get the hashed passwords out. So if you do a migration it will be painful to users since they’ll have to do a password reset.
Yes it’s cheap. But you get what you pay for.
Ory Kratos has a password migration hook that lets you migrate password credentials out of anything (including Cognito) without password resets. I believe most other (modern) auth vendors have an equivalent.
I really don't see any reason to be using Cognito in $currentyear.
Disclosure: working for Ory.