Honesty this just seems that we’ve lost a lot of operating systems except for POSIX and NT. Imagine a libcurl for a SmallTalk machine… or a custom RTOS without any POSIX comapt layer; I’d bet Windows will seem easy compared to one.
In fact, maybe the fact that a Windows port of libcurl can exist at all means that the Windows BSD socket implementation is useful enough to allow these sort of things.