Having digested the book a bit more, some more thoughts:
Happy to see magic item creation rules. Positive thoughts about magic items and tables mostly: I like the selection of common magic items - good balance of fun and useful without presenting balance issues. They subdivide magic item tables by rarity and some new category referred to as "theme": That is the categories "Arcana", "Armaments", "Implements", and "Relics". Which I presume refers to mage-type, warrior-type, rogue/utility-type, and priest-type treasure themes; but are evidently explained in the MM not the DMG. Which is weird and kinda counterintuitive. What I'm NOT seeing, though maybe I've missed it, is an overarching table of magic items by rarity. Which I'm not happy about.
On the other hand: There really is NOT a section for building monsters. There's a short and almost completely worthless a section about ADAPTING existing monsters. Seeing as how the monster building section was probably the second-most used part of the 2014 DMG by me personally after encounter-building, that is a pretty significant weak point. I'm going to be pretty angry if there isn't a robust creature-building section of the upcoming 2024 MM.