Citation needed, seriously if you make such broad, sweeping statements at lest back it up with specific evidence.
GNU glibc has some gratuitous extensions over ANSI C/C99.
Unix utilities have long non-standard and non-POSIX based flags.
So what? The OP wrote:
> Those hacks that allow for the ease of use in a GNU userland make programming a massive pain in the ass where nothing "just works" the way it should, because GNU programs and libraries are in flagrant violation of every specification and rule of thumb that has ever really mattered for Unices.
Just because the tools offer additional functionality does not mean they "violate every specification and rule of thumb that has ever really mattered for Unices" (what does that even mean?!). I mean you're welcome to edit files in ed, because that's pure Unix, but I'd rather use a more capable editor.
It absolutely does not mean "no manual programming or customization from the user required". It means no dirty hacks, like the ones mainstream distros employ to make some of the customization and programming unnecessary that is actually kind of inherent to the way Unix has traditionally worked.
That may very well be much less easy to work with from a consumer perspective, but from a systems programmer perspective it's the opposite way. Those hacks that allow for the ease of use in a GNU userland make programming a massive pain in the ass where nothing "just works" the way it should, because GNU programs and libraries are in flagrant violation of every specification and rule of thumb that has ever really mattered for Unices.
Also, it's GNU libc that has gone out of its way to fail to adhere to standards, not musl. GNU does not give a single crap about open standards, because they believe that whatever GNU is IS the standard, which apparently is your view as well. That's simply unacceptable for a lot of people.