His issues (from 3.5 years ago):

"- The string handling is braindead"

How so? Not a lot of specificity here.

"- The compiler and stdlib is immature. This seems like the first programming language the guy has written. You should have a few failures to learn from before you make a Serious Programming Language imo."

The Hare compiler isn't immature? As noted, this was 3.5 years ago.

"- Code run at compile time is a neat idea but has a weird syntax and really really complicates the internals of the compiler and related tooling."

And yet this has become one of Zig's strongest points.