My biggest complaint is static compilation. There are things you can do with PackageCompiler, but they don't work for some of the code I write. This makes deployment of artefacts harder than it needs to be.

Most of the infrastructure is there in the code, it just needs to be tied together, in such a way that juliac file.jl -o file.x results in a deployable (preferably static) binary.

To clarify (Correct me if this isn't what you mean), Julia compiles not only program code, but dependency code each time you run a program. This can make simple programs and scripts take a long time to start. A common response is "Use the REPL", where it compiles the dependencies once at load.

but its REPL is slow and not as interactive.