I teach IB Language and Literature. To succeed on their final exams, students have to be able to write two essays, in 135 minutes, analyzing two separate non-literary texts that they have just seen (for IB exam purposes, a non-literary text is basically a print text that is not a poem, story, or play - typically students might get a something like a review and an advertisement). Point is, they don't have a ton of time to analyze before they have to get writing, so we teach them the following acronym to get started: PAIRING.
Purpose: what is the text designed to accomplish?
Audience: who is it targeting?
Institution: who made it?
Representation: who is or is not represented in the text, and how are they represented?
Ideology: what is the explicit or implicit ideological bias?
Narrative: what story is it telling?
Genre: what genre features are employed or subverted?
We remind them to always start with the purpose - that's the one crucial element - and then focus on just a few of the other aspects, the ones that seem most obviously important.
So, the new DMG.
Purpose: The underlying purpose is...well, it's to sell books. But more specifically, it's to teach D&D players how to better run games. It's kind of right there in the title: it's designed as a "guide." So it's to sell books to D&D players who need a guide in how to be a DM.
Audience: I think this is the obviously important element of the DMG that spawns a lot of disagreement. A lot of it is geared towards inexperienced DMs. However, it includes other features (magic items, bastions) that muddy the waters a bit. I don't think you can realistically have "a DMG for all of us," but OP's suggestion that WotC publish different versions for different audiences is interesting. I think it would cannibalize their own base so I can't see them doing it, and in his case, I'm not sure why the 1e DMG doesn't suffice.
Institution: Wizards of the Coast made it, and they are a subsidiary of Hasbro. This has a lot of implications, because this is not some indie publisher releasing a kickstarter. This is a tentpole publication for a major corporation.
Representation: This could be a thread in itself, but suffice to say that WotC has made a pretty obvious effort to expand representation, especially through how it represents players in the text (e.g. non-gendered pronouns, using female players as examples as frequently as male) and visually (e.g. showing much more diversity in how characters are depicted).
Ideology: The new DMG is aggressively pitched towards a younger audience (new players) and is (arguably) framed towards younger ideological biases (c.f. representation).
Narrative: Most of the DMG is written from the perspective of a new player. This makes sense: I don't normally need a "guide" if I already know the paths.
Genre: There have been enough DMGs that it is arguably a genre unto itself, and we have certain expectations. The OP mentions Gygaxian prose. I think one of the reasons magic items are in the 2024 DMG is because they have always been in the DMG, even though to me they make a lot more sense with equipment in the PHB, or perhaps as treasure in the MM if you want to make Quixotic case that they should be kept out of the hands of players to preserve the mystery. In any case, I think many objections to the new DMG come from ways it subverts genre expectations (i.e. by reframing Rule 0 to be more about group consensus than DM control, though this is also ideological).