This results in miscompilations, broken buildins, features added that are then ripped out again.
I think fast iterations and experimental stuff are ok if you have a stable core. I.e. I don't mind if zig decides to change its for loop syntax after 5 years, so long as there is a simpler stable construct like `loop { break; }` that people that use the language in production and library maintainers can use.
You need a certain critical mass for a language to be self sustaining, and that requires people to actually use your stuff, which in turn requires at least some stability guarantees for some subset of the language.
Zig's response to that is "I'm just my inventors toy yet, but it will be grand when version 1.0 hits in 10-50 years."
The fact that they now want to replace LLVM with their own backend makes me think that even 50 years would be optimistic.