See, the thing is ... this disagreement isn't really about 5e. Which is why we are rarely getting either examples from 5e, or acknowledgement of what is in 5e. And there's a reason for that.
D&D, and 5e, is in a different position than any other TTRPG.
I keep saying this, but it needs to be repeated. When people say, "Hey, look at X rulebook. Look at how it does things ...." They are forgetting that there is an unstated premise ....
X Rulebook is for a game that is not D&D.
You have to start by unpacking what that means. By default, a person looking at X Rulebook for the first time and trying to learn how to play has never played that particular game before, and there are unlikely to be tables where that person can just join a game to learn.
This is different than the situation that D&D finds itself in. For D&D, it is (for most people)
trivial to find a game in person or on-line. Moreover, it is
trivial to find examples of people playing it. Finally, it is
trivial to find numerous additional sources, from videos to webforums to books for additional information on any subject that you want.
So you have to start with that premise- D&D isn't like the other games. In fact, the other games that are "guiding people through how to play" often have the advantage that many people already have a passing knowledge of TTRPGs because they have, at one point or another, played D&D.
This cannot be overstated- when people bring up these example, they rarely reflect on what they already know. I am always reminded of an example of a conversation I had here with an individual who always extolled the virtues of a particular very short rule set. And that person was right in terms of the ruleset (it's quite elegant and I like it). But what the person did not understand is that in order to run the three pages of rules, you had to (1) already know a great deal about playing RPGs, and (2) have a huge amount of knowledge about the particular genre and subject matter of those rules. The rules were only simple, easy, and elegant if you already had a base of knowledge going in.
It's like people are debating the best way to write a cookbook (think of the "setback" example). What do you have to assume? Does the person reading it know how to beat egg whites into fluffy peaks? How to caramelize onions? How to boil water?
People don't learn from books very well.
This isn't a universal point, and it's not just about "the kids these days." But the market for D&D (esp. for
brand-new players!) isn't the olds. And as a person who has taught a fair number of middle and high school kids in the last few years how to play D&D (so that they can then go run their own groups) I can reliably say that many of them use videos ... a lot. It's not my thing, and a lot of them use it in conjunction with reading (and a very few still prefer reading) but there's a reason that video and podcasts/audio are so popular.
In addition, you can't learn DMing by reading. No one does. You learn it by doing. It's the only way. A guide (as in a reference manual) can have things for DMs to refer to. But as soon as you start playing, that's what you're doing. Playing. Which brings up the third point.
The best format is the Starter Set or something similar.
It's fascinating that people keep bringing up Moldvay basic. I
love Moldvay Basic! But here's the thing about Modvay Basic for those who don't remember- it's incredibly limited.
It's only about Dungeon Crawls.
It's only for levels 1-3.
It had an example of dungeon design.
It was packaged with an introductory adventure.
Oh, and while it was pretty good
for the time (especially compared to the dense thicket of Gygaxian prose in AD&D), people often forget that it wasn't perfectly organized either- for example, buried at the end, in a part few people read at the time, was the "Dungeon Mastering as a Fine Art." In that section the DM was instructed that there was always a chance, and therefore could roll a saving throw, or assign a percentage. Also, there's always a chance, therefore the DM should let a character roll a d20 and roll under an ability score, with a modifier of some kind. .... I mean, cool, huh?
That said, the closest comparator to the acclaimed Moldvay text .... a very limited boxed set, aimed at beginners, with an included adventure? Yeah, it's a Starter Set. So if you are truly aiming to bring new players in, then you don't look to improve the DMG- you look to improve the Starter Sets ... which WoTC has been improving.
The argument for prescription.
The elephant in the room, of course, is that a lot of the disagreement is simply a desire to shoehorn in prescriptive elements. It's not about on-boarding new players or DMs- as a simple matter of actual evidence, 5e has been the most successful edition of D&D ever when it comes to that. Instead, it's a desire that WoTC takes a specific stance on
how people play D&D, with a desire that people
learn to play the right way.
And that is where the trouble starts. I want a game that welcomes all, and validates them. The Dungeon Crawlers and the Anime Fans. The resource managers and the storytellers. The optimizers and roleplayers. The people that love giant battle scenes with miniatures and the people that prefer quick and infrequent theater of the mind. All are welcome! And I prefer not to have people insist that the book start by saying I have to have a battlemap and miniatures on the first page just to play the game.
That's just me.