Extensibility can be nice, but the experience has a lot of friction. If you want something that isn't bog standard, you need to get or make an extension.

Making one is more work than what I can do from basic configuration settings in KDE. I want to spend my time on other projects. The marketplace suffers from the same problems as most marketplaces. Plenty of unmaintained extensions. No guarantees of quality. Now I need to do research on extensions instead of just changing a configuration setting.

The existence of extensions allows gnome devs to figure they don't have to support basic features because someone will make an extension for it.

Extension configurations don't live in the same place as standard configurations.

The experience is fragmented and has friction.

Well, I never wanted something standard so I always configured my desktop. My current GNOME desktop looks more like KDE than GNOME. I gave a try to KDE in 2014. It seems that it has been the wrong time to be there. I switched to GNOME Flashback (the one that looked like GNOME 2) and updated to 3 only when there has been the right extensions to make the desktop look like what I want it to be. Neither Apple nor Microsoft figured out what I want, so I use something else. Actually Microsoft have been closer to that with XP and 7 but it's Windows. I migrated to Linux in 2009.