> However I'd like to dig a bit deeper into the real value of this for a user of "stays with Emacs only Magit"-type.

That right there is the problem. I have been an Emacs user for decades. Magit is awesome because of Emacs, not inspite of Emacs. Whatever this person is saying, either they have not given any real thought to their own experience, or they really don't care about anything other than Magit as a piece of software that they prefer using. If it's the latter, then only that person can tell you what is so great about Magit. But that line of thought is really hard to understand and counter for a typical developer who cares about their entire coding experience and not just any one package.

> However, all those Doom users evaluating to move to "mainstream" editors, who do only minor adjustments (like options, keybindings), do they get something substantial from Magit that they can't achieve in those editors?

No. I would be very skeptical of people who make such claims.