ight there we see both the great advantage as well as the disadvantage of the DMG. On the one hand, as an actual text to prescribe a single way to play, or even for someone who has never played a single game of D&D (or seen a single game of D&D) to pick it up and start playing? It doesn't work ... at all. A brand new DM who never played, was unaware of youtube or twitch, and didn't get a starter set ... well, they would have little to no idea how to choose their own favored method to roll dice, or to choose the religion for their campaign setting. On the other hand, it served a much more important purpose - it provided both a toolbox, as well as being open-ended to allow most people to play D&D the way that they wanted to. Because the DMG didn't prescribe a playstyle, it also couldn't be weaponized against people that don't play that way!
I basically agree, though I think a potential future dmg could be better organized as a toolbox. For example, there are tables related to dungeon creation scattered among the "creating adventures," "adventure environments," and "random dungeons" sections. There is a section on "traps" that is not adjacent to any of those sections on dungeons. Xanathar's guide did a better job in terms of providing tools--the sections on (actual) tool proficiencies, downtime, magic items, common magic items, traps, and the names are all helpful, in some cases even if you aren't running 5e.
Some of the actual rules in the 5e dmg are a bit dubious. Some of this seems to be to appeal to fans of older editions. For example, on p. 127: "It's not unusual for adventurers--especially after 10th level--to gain possession of a castle, a tavern, or another piece of property. They might buy it with their hard-won loot, take it by force, obtain it in a lucky draw from a
deck of many things, or aquire it by other means." Really? How many 5e games features playing spending 20gp per day on maintaining an Abbey with 5 "skilled hirelings" and 25 "untrained hirelings"? And if you are going to run that type of game, the page or so of info here is not really adequate; you'll go to 3rd party supplements like the MCDM stuff.
So, yes, it is a toolkit in that sense, but it's a bit of a Jack of All Trades--the bard of the core books!
And then the layout. It's borderline unreadable, which is part of why no one reads it. Like, awarding experience is a core duty of a DM; it should be more than 2 columns of text long. And that text shouldn't be split across two pages and confusedly sitting next to the "madness" tables!