IMHO, YAML tries to be too clever. E.g. the fact that it happily guesses types and doesn't require strings to be quoted creates tons of traps.

    languages:
        - en
        - de
        - no
    portmappings:
        - 8080:80
        - 2222:22

parsing the above, "no" is suddenly a boolean, and YAML 1.1 parsers will turn "2222:22" into the number 133342 (because there was a helpful rule that thinks the latter means "2222 minutes 22 seconds" and turns it into the number of seconds... https://docs.docker.com/compose/compose-file/compose-file-v2... )

I really liked it initially, but after using it a bunch I'd prefer a more restricted subset of it. (also hit a bunch of parser bugs/incompatibilities, where the complexity of supported cases probably also plays a role)