(author here) in which ways does Gleam come short of that? Because I'm also looking for that middle ground and I was very curious to get a look at Gleam.

IMHO it's just that it's a beam VM language, which is a fatter runtime/ecosystem than is really needed to achieve the goal stated above can bring it's own bag of problems (but also it's own superpowers).

Also to be productive you have to utilize the rest of the erlang ecosystem, so at least some superficial knowledge in elixir & erlang is helpful for for some use-cases.

Syntactically I actually don't think it's that for off, but I dunno what GP was thinking, maybe that it leans more into functional patterns & sugar for those whereas rust/go can also be used in a procedural style. (Though at least personally I am using way more functional patterns in rust than I expected)