> ...no one I know is excited about working with GoF-style OO code these days

FYI, this is C#:

    var namedFunctions = new Dictionary<string, Func<int, int, int>>() {
      ["multiply"] = (int x, int y) => x * y,
      ["add"] = (int x, int y) => x + y,
      ["subtract"] = (int x, int y) => x - y,
      ["divide"] = (int x, int y) => x / y,
    };
    
    log(namedFunctions["add"](x, y));

This is also C#:

    var multiplyN = (int[] numbers) => numbers.Aggregate(1, (a, b) => a * b);
    var addN = (int[] numbers) => numbers.Aggregate(0, (a, b) => a + b);
    var subtractN = (int[] numbers) => numbers.Aggregate(0, (a, b) => a - b);
    var divideN = (int[] numbers) => numbers.Aggregate(1, (a, b) => a / b);
    
    log(multiplyN(new[]{1, 2, 3, 4}));
    log(addN(new[]{1, 2, 3, 4}));
    log(subtractN(new[]{1, 2, 3, 4}));
    log(divideN(new[]{1, 2, 3, 4}));

As is this:

    // Return a tuple
    var runCalcsAsTuple = (int[] values) => {
      return (
        multiplyN(values),
        addN(values),
        subtractN(values),
        divideN(values)
      );
    };

    // Destructure the tuple
    var (
      multiplyResult,
      addResult,
      subtractResult,
      dividResult
    ) = runCalcsAsTuple(new [] {2, 3, 4, 5});

Named tuple types are also kinda interesting:

    using Profile = (
      string Username,
      (string Hn, string Mastodon) Socials
    );

    var profile = GetProfile();
    var (hnHandle, mastodonHandle) = profile.Socials;

    Profile GetProfile() => ("chrlschn", ("CharlieDigital", "@chrlschn"));

If you haven't looked at C# in a while, I'd recommend taking a look with a fresh set of eyes.

Small repo with examples comparing C# to JS and TS: https://github.com/CharlieDigital/js-ts-csharp