For me, the magic in Magit is how its interface is perfect for new users as well as long-time power users: new users get helpful menus to show them what options are available, but the menus display instantly and are entirely keyboard-driven, so that long-time power users who know the keystrokes by heart are not impeded one whit. There's no trade-off between power tool and beginner-friendliness here: everyone gets all the goodness all the time.
The interface builder has since been spun out as a separate library (and now included with stock Emacs!) called Transient, so there are several packages that leverage it. My favorite LLM interface (gpt.el) makes heavy use of transient menus. I've created my own transient menus for thinks like my PKM (Denote by Prot), my LSP client of choice (Eglot), and my citation manager (Citar).
The interface builder has since been spun out as a separate library (and now included with stock Emacs!) called Transient, so there are several packages that leverage it. My favorite LLM interface (gpt.el) makes heavy use of transient menus. I've created my own transient menus for thinks like my PKM (Denote by Prot), my LSP client of choice (Eglot), and my citation manager (Citar).