Honestly I don't even disagree with you. I think POSIX sucks. I think even the libc sucks. However there is no way you can look at the Windows API mess above and think it's somehow better than the portable and clean getenv function call. Maybe you can "get used" to that cruft but I can't. If I had to deal with code like that the first thing I'd do is abstract it away so I don't have to deal with it anymore. That's exactly how Windows is and should be treated by everyone.
Video games, your counter example, are probably the most platform-specific software imaginable. There's a reason pretty much everybody uses an engine these days. There is no way you can compare that stuff to getting a user's home directory and writing files in there.
Also, for video games it ultimately doesn't matter how sucky the APIs are since it's all about market share anyway and people will use whatever they need to get it done. First parties don't put in effort into porting games to Linux because they don't see the money. Valve puts in effort because it gives them their own platform that they control and therefore leverage over Microsoft and its app store. Emulation and compatibility layers are a proven solution when first parties aren't playing ball. If they don't want to make it work on Linux, people will make it work whether they want it or not.
Just because you aren't used to it doesn't mean it's 'bullshit'. Might I provide a counterexample to the 'simplicity' of Linux? Developing video games natively on Linux is such a pain point that the industry has standardised around simply translating Windows syscalls and Direct3D shaders to their Linux equivalents, because the latter is so heavily fragmented to develop natively for. Also known as Proton.
[0]: https://en.wikipedia.org/wiki/C_POSIX_library