I love Rust for mathematical and scientific tasks (I am building the structural bio crate infrastructure), and I love Mathematica and have a personal sub. I should be the audience, but... What makes Mathematica great, IMO, is the polish and overall experience created by consistent work with applications in mind over decades. So, I look at this project with skepticism regarding its utility.
Similarly I'm not sure Octave ever really got that polish to compete with MATLAB.
SPSS is hilariously painful to use. Still it's only losing ground ever so slowly. PSPP remains almost unheard of among SPSS core users.
Yeah, the Mathematica language is the least interesting aspect of the Mathematica system. Closely followed by the interactive notebooks.
Half-assed reimplementations of existing software (often in the name of "memory safety") is what the Rust community is best known for.
Sure, but you've got to start somewhere! And with the amount of progress I was able to make in just a few weeks, I'm very optimistic that the polish will come sooner rather than later.