billd91
Not your screen monkey (he/him) 🇺🇦🇵🇸🏳️⚧️
How to organize best depends on how most people are looking through the Monster Manual. An alphabetic arrangement that includes the monster's stats is best for quick reference at the table while running the game and/or when you know the name of the creature you're looking for. For those purposes, I'd argue an alphabetic arrangement is by far the most efficient arrangement, particularly for quick reference at game time by a DM - the time when efficiency in lookup is at its greatest need.Because these creatures are invented and their names random, all the more reason to organize by Creature Type, which assigns at least some kind of meaning for those searching.
Pretty much every other case - whether designing an encounter, populating a dungeon, building a wandering monster list - has much more relaxed efficiency needs and can make use of supplementary indexes sorted by other criteria.
And in this sense, the Monster Manual is a bit inconsistent in breaking out vs grouping monsters in its alphabetic arrangement. So I get the OP's frustration.