It's not the "what", it's the "how". Magit enables extremely fancy workflows with great simplicity, and its UI is self-discoverable and well laid-out. Magit has the best UX of any git tool.
Which others have you tried?
The way you described Magit is exactly how I would describe SmartGit and also the built-in git features of several IDEs, including the Jetbrains family and Visual Studio (although I dislike Visual Studio because it's slow).
For me, Magit code staging is the best I've tried: staging whole files is as easy as staging single lines, which means my commits are more meaningful. Magit also allows me to use some fancy features without having to remember they exist, thanks to the well-thought command popups. Last, it's integrated with Emacs: this means I can move through code and write my commit messages in a familiar, coherent way.
The final advantage for me is that Emacs and Magit are forever. They will live longer than any other tool out there.
Check out Orgzly from F-droid repos.
There are lots of tools I'd use if I weren't programming for work and didn't have a team of mixed technical skills, and perhaps Emacs fits into that category.
Lots of editors have git plugins. The question is, what can you do with magit that you can't do with those?
> slime
This is a pretty niche need, but sure. I would agree that people writing most Lisps (excluding Clojure) are better off using something like Emacs.
> Org mode
The fact that my editor doesn't have this is a feature for me. I want something with a clickable GUI that syncs to my phone, gives me reminders, and can be shared with coworkers when necessary.
I've recently been using ClickUp, and it's been fantastic. I can run it in a window next to my editor. I'm not sure what the setup is missing that Org mode doesn't deliver, but I do know that Org mode is missing a lot that ClickUp gives me.