> I still think the world really needs a solid, immutable-first and functional-first scripting/glue language, and Crystal isn’t that.

The author might be interested in Roc [1] by Richard Feldman et al, which seems to check all the boxes, including scripting with type inference and glue with good FFI to other languages. It is still in early stage, though, since it is a very ambitious project.

[1] https://www.roc-lang.org/