Apple seems to have solved this with a combination of big community of enthusiasts and an App Store for macOS, and just the App Store for iOS. A major fear of Apple developers seems to be the prospect of their App being removed from the App Store for unclear reasons.
It's hard to imagine a model where apps can remain FOSS but have the same sort of strict design guidelines.
I come from a background of early MacOS, NeXTSTEP, and the Newton, three environments which prided themselves on developing novel and useful interfaces tailored to the specific needs of their platforms. The X11-inspired cross-platform toolkits are head-shakingly bad compared to these efforts. For example, GTK on Maemo was so embarassingly inferior in design to NewtonScript (a GUI 10 years before it note) that I wrote an entire article about it.
I think the only decently crafted open source UI on Linux/BSD right now is Android. Because Google has the resources and heft to make people do it right.
Also Qt is fairly independent of X11. It can operate fully independently from X and nowadays is basically agnostic to X. I suspect GTK is similar.
Windows came out in 1985.
CDE came out in 1993.
> Also Qt is fairly independent of X11.
You seem to be missing my complaint. By supporting multiple platforms, Qt is forced to support the lowest common denominator of all of them. Which means it's mediocre on all of them. Being cross-platform is fine: but no cross-platform systems can be held up as paragons of UI design excellence, not by a long shot.
Eh? MacOS had the same tools, and until quite recently the Mac App Store wasn't even a thing (and, even today, the presence of, say, Slack, or the LG monitor utility, in the App Store would argue that Apple is not particularly worried about UI stuff there...)
MacOS (capital M, no space) is generally classic MacOS, 1984-2001.
macOS (small m, no space) was formerly Mac OS X, later OS X, sometimes quoted as Mac OS (note, space between Mac and OS).
MacOS: 1984-2001
Mac OS X (formerly NeXTstep): 2001-2012
OS X: 2012-2016
macOS: 2016 onwards.
and macOS is still Mac OS X in places.
But yes, by MacOS I had meant the original.
You won't be able to make everything consistent but you can make everything at least look unified.