Was "yellow box" ever anything but vaporware? I spent some time fiddling around with Macs from that era and never heard of it before today. I remember almost getting an eMate for a portable laptop a while back, but they were never as cheap as they ought to have been considering the usefulness of the hardware. (Instead I bought an X61 which is still my main laptop...)
I had to really dive into some old NeXTStep documentation some months back because reasons. I would love to read a history of how they got from that to modern OsX from someone who had been around since NeXT. I totally understand why people who worked with NeXT boxen are nostalgic for them, and baffled at how it evolved into the seriously abusive development environment Apple offers now.
Sure, but indifference isn't malice. They didn't want to suck for the NeXT crowd. They actively courted them; prior to being the iPad/iPhone company they were all "hey guys we're still a real Unix, look, we'll even release Darwin for you to play with." So yeah, of course part of the answer is they got painful to work with because not being painful to work with wasn't a priority, you'll put up with it because that's how you sell apps. That's true of Windows too. Windows started off with crap though, and they tried to fix it with NT but then they just had something clever emulating crap. Apple started with NeXT, and while they don't have a compelling reason to go out of their way not to make it suck if you don't buy computers because they're pretty, they've never had an obvious reason to make it suck. Nor, until the last few years, have they had a hard time hiring good engineers. Yet somehow they went from being more clunky than linux but tolerable because it's convenient to be running the same OS as the designers and accountants and secretaries when I first got exposed to it to... not.