I like my monster books with lots of descriptions, adventure hooks, and material that helps me put these monsters into the game. I think the statblocks are secondary.
For example, I consider the 2014 Monster Manual section on Hags stellar. It is packed full of adventure hooks, each of which can be mined for a full-blown adventure, and it is also full of advice for how to portray them (descriptions, mannerisms, names, etc.). The blurb on Monstrous Motherhood alone basically describes an adventure ready to run, and I have done so across multiple groups, and it's always been a great hit.
Volo's Guide to Monsters takes that to the next level and gives me pages upon pages of gameable material to pair with hags. I can run a full campaign just with this material. Volo's, Mordenkainen's Tome of Foes, Fizban's Treasury of Dragons, and Bigby's Glory of the Giants are all absolutely wonderful and I do not part with them. My Tier 1 adventures always rely significantly on Volo's first chapters. I'm still shocked that they retired the first two in favor of the much blander, much less useful Mordenkainen's Monsters of the Multiverse.
The statblocks in the 2014 Monster Manual are perfectly serviceable, especially when paired with the lair actions and alternative statblocks described in Volo's and Tome of Foes' specific monster sections . Are there better ways to capture the monster with flavorful abilities? Sure. Tales of the Valiant does a good job in its wonderful Monster Vaults (highly recommended), especially related to fiends. But the internet has about 500 different 5e versions of the each MM monster, all of them free, or I can just alter them on the fly, which is fairly easy with a system as adaptable as 5e. The important part is the advice on how to build an immersive adventure around them.
After Fizban's and Bigby's, I hope James Wyatt keeps going and writes other type-focused monster books. I'll be buying them.