Ansible must examine the state of a system, detect that it is not in the desired state and then modify the current state to get it to the desired state. That is inheritently more complex than building a immutable system that is in the desired state by construction and can not get out of the desired state.
It’s fine as ,one as you use other people’s rules for ansible and just configure those, but it gets tricky fast when you start to write your own. Reliably discovering the state of a running system is surprisingly tricky.