Ultimately, the question you are opening is what belongs to the core, what belongs to core extensions, and what should be just third-party. The way I understood the Flarum 'vision' is that the core is mostly a developer framework with the most basic tools that any forum would need. The core extensions add all the basic bells and whistles that most people would leave enabled, and for all other things, there are third-party extensions. As a result, the core stays clean, which leads to more effective maintenance down the line. Flarum itself becomes more of a developer framework for online communities and forms the stable API that will lead to a feature-rich ecosystem that is more interesting for developers and people wanting to run their communities on this stable ground.
The lack of live preview is subjective. Personally, I don't mind it at all and a WYSIWYG extension exists. A basic file uploader may as well be a core extension, I agree here, but I don't see it as a significant issue either since fof/upload is well maintained. I believe better support for some basic light/dark mode support in its core is planned to some degree, but once again, fof/nightmode is perfectly maintained. I'm more neutral on the PWA stuff; I think it's more niche, but I may be wrong. Once again, has there been a specific issue with the extension?
Regarding the risk of them being abandoned, that's the point with the fof extensions. They are basically first-class supported extensions that have a very low risk of being abandoned.
GoodTimes In my experience, people are eager to submit fixes and improvements to the main software repositories, but if they find a bug in an extension, they're more likely to disable and avoid the extension instead of trying to fix it. This is a significant issue.
I don't understand this perspective at all, and from personal anecdotal experience, I would claim the opposite. The main repositories often seem a lot scarier to touch, whereas a smaller, less official extension might seem less intimidating to submit PRs to. Touching a behemoth that lots of people depend on is more daunting than an isolated extension doing one thing.
