Given that YAML it's a configuration language I'd say that not being turing complete it's a feature, not a bug nor a limitation; I always want my language files to be declarative to not suffer the perils of logic.

Edit: Also, I don't see the need for a turing complete language for something like docker compose, if you need something really complex you can always script a docker-compose.yml generator with all the logic and complexity you need.

You might find Cog (https://nedbatchelder.com/code/cog) helpful for generating YAML on the fly.

When I need a Turing-complete Compose file, I use Pulumi to spin up the Docker containers and wire things together: https://www.pulumi.com/blog/pulumi-and-docker-development-to...