Git Extensions is amazing. Too bad it's only for Windows. As nice as Magit may be, it would be even better as a standalone TUI application. I don't want to have to learn Emacs to use it.
Magit would make no sense outside of Emacs, because it's not just an extension - it's also a bunch of libs anyone can use - the way how Emacs works allows you to re-use and modify any behavior of any function with extreme granularity.
Practical example - while browsing GitHub in my browser, with a keypress I can let Emacs grab the current thing and operate on it - clone the repo, read files, review PRs and Issues, etc. I can even do these things directly from my notes, or when someone shares a url with me. This isn't part of Magit, these are my own customizations, but it would be much more difficult to achieve without Magit.
It's definitely not perfect but it's good enough to work for basic committing/rebasing flows and it's faster than booting up emacs for the same purpose.