Personally, I find yet another monolithic kernel unix clone is not what we need, but the point here is that it's made in Rust, which itself is an experiment; It is best to not do too many experiments at once, thus cannot complain.
It seems highly irrelevant what you or I need. The author explicitly made the project as a learning experience, not for others. The "Why" is described in the opening paragraph, and makes the goal very clear.
And it seems like the author was highly successful, so congratulations author! Great to see people diving headfirst into very complicated parts of the stack.
There is no need to twist my words into sounding negative.
As already explained in the parent, congratulations to them for getting it done, and I believe it does provide value through testing one thing (Rust) while sticking to the very mature and well understood UNIX design.