People working on most components of the desktop Linux stack are being paid for it. Think kernel -> video drivers -> systemd -> wayland -> GNOME. All of those groups have paid employees. They are evidently understaffed.
Obviously, a lot of paid work is done on low-level plumbing, because Linux is hugely profitable as a server, infrastructure, or embedded operating system for a lot of companies. Graphics infrastructure (KMS, Wayland, X11, etc.) is useful for companies who embed Linux in various appliances (set-op boxes, etc.). Red Hat probably invests in GNOME because for Red Hat Enterprise Linux Workstation and dogfooding.
If your programmers can make your project their job, you don't have to worry about the amount of time they have to contribute.
Walled-garden hardware like Apple has set up certainly has advantages, but given that windows is installed on a far greater variety of hardware than linux distros, I'm kinda surprised its more stable. I guess other than the obvious fact that everybody working on a given linux distro is doing it for free (right? that's my impression).
Most of my troubles vanished when I switched from Ubuntu to Debian. Only been about two weeks but loving it so far. Might finally be able to abandon OSX!
(note: I'm a total noob when it comes to OSs and whatnot - not that kind of programmer!)