AFAIC, 4E's DMG, is the best DMG written to actually teach a DM how to run the game. 5E, 3E, 2E, and even 1e (though my personal fave) all pale in comparison in this regard. And generally the best parts of the 5E DMG, are lifts (sometimes word for word) from the 4E DMG.
It’s really a shame how many people allow their absolute hatred of 4E to convince themselves that absolutely everything in the Edition was wretched and should be rejected not on its own merits, but just because it was a part of 4E.
There are a LOT of good things that 4E came up with worth preserving and the DMG’s “DM advice” is definitely one of those things. Which, as mentioned, 5e lifted and tried to pretend was it’s own innovation.
5e did a lot of that. I still remember that article from Monte Cook’s when he signed on early in 5e’s development where he tried to sell Passive Perception as this revolutionary new thing they’d only just come up with... that had been part of 4E from Day 1. It got him roundly mocked, but was also one of the earliest indicators that the 5e dev team intended to fully throw 4E under the bus and claim that anything that was lifted from 4E was first invented by the 5e team.
Honestly, the part I miss most from 4E was the extensive work it did on reimagining a lot of the fluff to create a much more useful default setting than the standard D&D setup.
Even there it was such good work the 5e team cribbed from it. The 4E World Axis cosmology was so effective that even 5e stole the primary aspects of it (the 5e Great Wheel is basically 4E’s World Axis with the Great Wheel dropped into the Astral Sea in place of an archipelago of islands/divine realms (that were the great wheel planes just not in a wheel formation).