I do think that the 4e DMGs were fairly clear about how to run 4e. IMO, the DMG 1 initially stumbled a bit with things like skill challenges, but I, nevertheless, think that these books showed a good deal of clarity and self-awareness about how to run 4e. What is also remarkable for me is how often I have seen some 5e influencers and content creators recommend the 4e DMGs as solid books with advice for running their 5e games.
I would argue here that 4e probably had a clearer grasp and articulation of the predominant contemporary play culture of D&D.
By all accounts the 5e DMG is not that good (I've not looked at it myself), so that last point doesn't surprise me.
I'm from the school that thinks the 4e DMG is better than many RPG books, but that it could have been better. For instance, Worlds & Monsters has terrific discussions of the gameplay and thematic logic of various places and planes, of gods, and of various creatures and creature types/groups, but the 4e DMG doesn't replicate this much at all: it has first rate tactical encounter building and resolution advice, but the only bit where it talks about the
fiction of the game from the meta-perspective is its (very good) discussion of languages.
Another example of what I find a bit weak: in the Rules Compendium skill challenge example, the final check fails, and thus brings an end to the skill challenge (as the third failure). The check is a Streetwise one, to identify/obtain information about an old building that is connected to a matter the PCs are investigating. The consequence of failure is that some NPCs, whom the PCs successfully brushed off earlier in the challenge (via successful Intimidation) turn up, better armed and with a tough friend, ready to beat up the PCs.
Now that's an excellent consequence, but it doesn't follow simple causal logic, in that there is no immediate causal connection between
attempting to recognise a building and recall urban legends about it and
your enemies turning up ready to fight. The connection is more about theme and stakes and bringing it home when the dice say that you can. But the book doesn't explain or analyse this at all: it presents it as if it's self evident. But endless threads on ENworld make it clear that it's not self-evident at all.
This is where I find my "bibles" help - they have much more overt, "meta"/process-oriented discussions of these techniques.
HeroWars/Quest and Maelstrom also talking about how to use free descriptors in resolution also helped me a lot in understanding how to use powers and gear (including magic items) in improvised actions both in combat and skill challenges. Although 4e uses keywords rather than free descriptors, I still found those discussions extremely helpful. But for them, I don't think I would have seen or been able to successfully adjudicate as much creative and imaginative stuff as happened in my 4e play.
I guess the flip side is that the more overt the 4e rulebooks, the more they frustrate/irritate some people. And I'm sure you've participated i threads where I've posted the crystal-clear stuff about player-authored quests and seen "trad"-ish interlocutors try and explain how it's nothing different from a GM-gated "sidequest"; probably any attempt by WotC to explain stakes, consequences, "make your move but misdirect", etc would have triggered similar scepticism.
But from my perspective that's WotC's commercial problem, not a problem for me as a RPGer to worry about.