It may look good --- beauty is in the eye of the beholder --- but it's ergonomics are bad. All those hamburger menus, all those disabled configuration parameters, the non-modular architecture, the poor state and quality of Gnome Shell extensions. I really try to like the modern Gnome, but they make it very hard. If your goal is not staring at some graphic design, but having tools that help and do not stand in the way, then Gnome feels just wrong. The primary reason why I still try to work with it, is its integration into system services.
Completely different experience here. At least for my purposes everything is exactly how I want it. I really have think a lot to come up with an issue for the GNOME Environment, except that some applications aren't ported to GTK4 yet
Honestly, the real hurdle now seems to be the support for paid apps. It's such a taboo in the Linux world, for some reason [1], but thankfully Flatpak and Flathub are working towards that goal [2], which ElementaryOS already explored.
I want small, high quality apps like macOS has. I want to make a living building open source software that can be supported and bought commercially—no, donations and sponsoring isn't good enough. I want companies being able to sell their software on Linux through the integrated app store, now that it's finally become good enough.
1: Plenty Linux users think FOSS means never having to pay for software, or that commercial software will kill us all and it's morally wrong. I strongly disagree.
It's "supported" just fine now. You certainly don't need some centralized app store or weird quasi-distro. As you say, it's 100% a cultural problem. No amount of technical effort will change that Linux users expect their software to be open source, and that in practice you cannot sell open source software.
The HIG are excellent, without GNOME I would be maybe 40% as productive as with it.