You can automate IIS configuration with Ansible, that's what we do.
Mostly the issue is documentation, you sort of have to know what things are called, but you can get around that by using win_iis_webapppool and get the configuration from a running IIS server and then work out which properties you can set.
There might be things you can not automate, we don't use that many advanced features.
Edit: I wasn't being fair. Ansible, is actually pretty good at managing Windows servers. It's just different from managing Linux servers.
Mostly the issue is documentation, you sort of have to know what things are called, but you can get around that by using win_iis_webapppool and get the configuration from a running IIS server and then work out which properties you can set.
There might be things you can not automate, we don't use that many advanced features.
Edit: I wasn't being fair. Ansible, is actually pretty good at managing Windows servers. It's just different from managing Linux servers.