I must be doing something wrong, because when i run the playbook I get an unconfigured nginx page at the ip of my server.

The instruction docs for ansible states:

Do not edit anything inside the {{ }} braces.

https://github.com/LemmyNet/lemmy-ansible/blob/main/examples/config.hjson

however that config file points to:

https://join-lemmy.org/docs/administration/configuration.html