I see no way a single book can cover everything for everyone. It's not a tutorial book, it's not meant to be. On the other hand you have text from a random chapter I rolled the dice and got a 4, Creating Non Player Characters. The intro to the chapter:
A nonplayer character is any character controlled by the Dungeon Master. NPCs can be enemies or allies, regular folk or named monsters. They include the local innkeeper, the old wizard who lives in the tower on the outskirts of town, the death knight out to destroy the kingdom, and the dragon counting gold in its cavernous lair.
This chapter shows you how to flesh out nonplayer characters for your game. For guidelines on generating monster-like stat blocks for an NPC, see chapter 9, "Dungeon Master’s Workshop."
Someone who has DMed a previous edition doesn't need this, a new DM might. So it is objectively clear that it does have
some things for the new DM. Whether it's enough is a subjective judgement. I don't see any indication that it's particularly "tilted" toward DMs from previous editions, there's little or no* discussion of previous editions or how they relate to the current edition. I would also agree it's not a starter set.
It says what it's purpose is on the back cover
Inside you'll find world-building advice, tips and tricks for creating memorable dungeons and adventures, optional game rules, hundreds of classic D&D magic items, and many other tools to help you be a great dungeon master.
The second paragraph in the introduction to the book states
The Dungeon Master’s Guide assumes that you know the basics of how to play the D&D tabletop roleplaying game. If you haven’t played before, the Dungeons & Dragons Starter Set is a great starting point for new players and DMs.
The book is quite clear on the target audience. Someone who has never played the game before is explicitly not it. Yes, people will complain that you have to spend an entire $20 to get a starter set, but considering the incredible amount of entertainment I've gotten over the years it's an incredibly cheap hobby.
*
I can't think of any but I don't have the book memorized.