I probably sound like a broken record at this point, but I would love to see less "always" and less "one size fits all" thinking appliesd to a monster book.
Maybe the kobold section has 2 lines of stats like
@overgeeked 's griffon example, and then gets into tons and tons of traps & ways the kobolds interact with traps & maybe some collective lair actions that attack your gear/light sources/separate the party. Whereas the sphinx section might also have a very pared down stat block and instead be rife with trials / riddles / tests of the worthy. The mimic section might have a random table of unusual mimics. And the bulette section stays about how it is in the MM.
One thing I adore about Skerples'
Monster Overhaul book is that there's a lot of attention to what the GM is going to use that monster for. Knowing how the kobold or sphinx is different from the mimic or bulette – and designing its monster entry toward that ideal/common usage is what I would like to see.
Most monster books (not just talking Monster Manual) for 5e cling to the standardized format, and I think it actually restricts creativity and pushes the game even more towards being primarily about fighting. I get it, it's D&D, but there actually are tons of really cool lore bits that never manifest in the monster stat blocks.