You probably need to create an inventory (https://docs.ansible.com/ansible/latest/user_guide/intro_inventory.html) with all of your machines in it, then when you run your playbook you can run it against all of them, or a subset (host or group).
You can specify custom variables in your inventory at your host level or at a group level, so you don’t need to have a specific include_vars task if you don’t want to.