On the other side of the scale, this codebase started in Zig from 5 years ago while the Zig of today is still very much pre-1.0 - still in the middle of things like finishing up moving to a self hosted compiler. Things like binary size, performance, or some of the oddities around drift in the language (like the custom macros vs now built-in language features) in this rewrite are not really as bad as they'd seem if this was a port from a more complete language.
That said, I think the parts around wanting to properly have memory safety guarantees rather than try hard & patch as issues are found is a more serious concern for Zig as those speak more to the design goals than the current implementation. "better safety than C while maintaining C compatibility" may not be a very compelling reason to chose Zig if other languages are able to do that portion better anyways, even ones without a GC.
That said, I think the parts around wanting to properly have memory safety guarantees rather than try hard & patch as issues are found is a more serious concern for Zig as those speak more to the design goals than the current implementation. "better safety than C while maintaining C compatibility" may not be a very compelling reason to chose Zig if other languages are able to do that portion better anyways, even ones without a GC.