First, UFW only exposes a small subset of iptables functionality through its UI, if you want anything else you'll have to add it manually, which is error-prone. And UFW can't (or couldn't, when I last looked at it) read config from multiple files, which makes it really hard to build up configuration declaratively & separate concerns. When deploying using Ansible you want to be able to add rules for different services independently, which is easy using Ferm as that reads config files from a directory, but very difficult using UFW.

Also, disabling UFW by accident can happen quite easily, if you e.g. remove your systems' Python version (to install a new one) it will uninstall UFW as well, opening up all ports & chains in the process. On a desktop system that might be OK, but it's just not acceptable for a server system IMHO. Hence the first thing I do in any Ansible base role is to remove UFW and install Ferm.

Ferm isn't perfect either but it has much better support for most iptables functionality and the way it builds up and applies rules makes it way more suited to a production environment.