Earlier quoted context omitted.
There's always been some leeway in that. Both the original Mac OS and Windows had a variety of languages targeting it, but they tended to strive towards emulating the core SDK experience (if they weren't a wrapper around it). Unix had it different with there being no core experience in the first place -- X11 being a glorified terminal multiplexer plus xeyes. Whether it was the commercial Unices with OpenLook/NeWS vs…
Hence the opinion Steve Jobs had about UNIX, NeXTSTEP's POSIX support being more geared towards bringing software in and win DoD contracts than anything else. I don't need such vision, it is how it would look like if all OSes happen to jungle browser instances, ChromeOS style, while a big chunk of applications runs on someone else's computer, abstracted via language runtimes. The return to mainframe's timesharing day…
The reason apps all went cross platform is that desktop operating systems stopped innovating. Which is the desktop platform with the most new native apps, where developers take pride in making non-cross platform experiences? MacOS for sure. Which desktop OS has been consistently the most innovative over the past 20 years? MacOS!
Haiku running IntelliJ is technically interesting, but ultimately as a user I don't understand why I'd want to use Haiku. BeOS may have been innovative 20 years ago but it's a dead OS that hasn't changed in decades. May as well run IntelliJ on any other platform, then.
I think the desktop can be great again, but it will take a new generation of developers with new ideas about where to take operating system technology. I also tend to think that whoever tackles that problem will probably tackle it by writing a cross-platform app runtime that slowly expands to become more and more of an operating system until the actual OS is indeed, just relegated to providing some drivers and bootstrap code. But the actual UX will be defined entirely by that environment. Sort of like how Pharo gives you a full blown desktop environment when you start it (but I'm not arguing for Smalltalk)..