Its just a matter of repetition. It will eventually click if you go back enough times (at least it did for me after like 4 tries). The biggest thing to getting your mind adjusted to the syntax is to understand that nix is just 1 big JSON blob. All the syntax is there to facilitate merging/updating that ball of JSON in a deterministic way.

You might try to generate your docker containers using nix as a first step. Not sure if it will be more approachable for you, but at least its 1 less new thing to adjust to.