The packages-first attitude feels significant to me. A language that “users” enjoy but package developers also enjoy seems important. I hadn’t thought about language choice from a heavily package-development weighted perspective before. It seems obvious in retrospect though, which is probably a sign of something cool.

A version of this would be: how can good package development be as easy as possible, and how can package use be as easy as possible?

I haven’t done any serious work in Julia mainly because the python libraries are mature, good, and performant enough. I can’t speak for everyone, but for end users in science labs library support is perhaps the biggest consideration for language choice.