I don't think you understand the scope of what you're talking about. Linux is tens of millions of lines of code, most of which is drivers that have to be written by vendors.

Vendors aren't going to write drivers for your hobby kernel. No one is using your hobby kernel. Bootstrapping a new kernel without billions of dollars to invest in development time is almost impossible, and anyone who is investing billions of dollars is likely going to have dubious proprietary reasons for doing so.

A successful kernel is Rust is probably the worst thing that could happen to the open source community.