However, given this library seems to be about passing NumPy arrays to/from Julia, the application is almost certainly to expose numerical stuff from Julia to Python. Basically, the use case is similar to Numba, but it works by producing a C-extension from a Julia system image (if I understand correctly). The main advantage over something like Numba would be access to the Julia ecosystem.
In contrast, if your performance bottlenecks are IO, parsing and hash table operations, then Julia's performance will be in par with Python and get absolutely crushed by Rust (I have less experience with C, but would imagine Rust and C are about equally fast).
The major difference with Python is that Julia's implementation of these things _could_ be fast in a way that Python's can't. They just aren't.
Though I agree parsers haven't gotten much love in Julia. That said, this repo is saying it's for implementing NumPy extensions, and I don't think NumPy has many parsers it's using.
Anyway, I think it might be a good exercise for me to make a repo with a few test cases of where I think Julia could use some optimisations, and compare to Rust and Python.
Try timing Julia's IO, or it's string processing, or it's hash tables, or its array allocation or it's GC - you know, nearly everything other that mathematical operations on floats or ints. Nearly everything leaves performance on the table.
Sure Julia is fast, but not on a C level in these areas. There is still lots of room for optimisation, though.