As an aside - D, Zig, Rust, even typescript got most of the lessons learned from C right
Zig has the (in)famous "Writergate": https://github.com/ziglang/zig/pull/24329
And besides Rust's high count of RFCs, there are things like async (I'm not complaining about it, but its an obvious large-scale "change"), module system changes, etc.
(To be clear, I like both languages a lot. But I wouldn't call them slow moving or right from the start.)
When I started building a Lisp-based machine learning framework, Guile seemed like the right choice because it provides GOOPS and generic functions, yet I still ended up with a lot of boilerplate to compensate for the lack of a strong type system.
Scheme feels to me like C is to C++: not ergonomic for large-scale application development. Go is one of those languages that has both minimalism and productivity.
My best litmus test these days is support for multidimensional arrays because it's always needed at some point in general purpose languages. CL and Ada had it right from the start while C++ needed C++23/26 to get std::mdspan and we still need to wrap it to pass the underlying/owned memory pool around (https://rosettacode.org/wiki/Multi-dimensional_array for more).
Hopefully next they can add some error handling syntax and controls.
I like CL, but I can't agree that a stdlib that doesn't even have a string split function is batteries-included.
The hard part about making a language is creating the stdlib and tooling and support for the language, but actually creating a language itself that has more features and better features than go can be done by a single person in a few months or a year probably, depending on how much experience they have.
Generics specifically are a great example here. A single person can implement a language with go-level generics fairly easily.
Objective-C in contrast was a very few additions thoughtfully added that composed cleanly and freed the programmer to actually get things done.
-- Greenspun's tenth rule
He had some lack of conviction to scope it so narrowly.