After digging through an issue we have, #362 I noticecd if I remove ansible-vault from my enviroment ansible begins to work.
Looking at the code, it seems a simple boolean option in the checkAnsibleVault() function in https://github.com/rundeck-plugins/ansible-plugin/blob/main/src/main/groovy/com/rundeck/plugins/ansible/ansible/AnsibleVault.java to force the function to fail will make rundeck bypass the ansible-vault bits of the code.