But JS isn't, so people look for other languages to fill the gaps. They seem to often settle on Rust, but it pays a relatively high productivity price to get those properties without garbage collection.

Is GC a problem in language analysis systems? Doesn't feel that way these days, and anyway JVMs have pauseless GCs anyway now.

I don't think GC is an issue, pauses would usually not even be noticed by the user.

In terms of speed, as long as you don't choose Python I think you'll be fine.

I do think in terms of productivity, something like F#, that has GC, ML style syntax with piping and partial application, and a strict enough type system with Hindley-Milner type inference, would be the most productive.

My hold up was mostly with the sentence I quoted which seems to contradict itself.

I agree it was an ambiguous and poorly phrased sentence.