I'd be quite happy with it your way - I'm not advocating removing things that people might want (I just don't know why anyone would want the old versions of the monsters, and I expect that anyone who does will be in a tiny minority).
The old versions of the monsters/NPCs were designed with reasonable parity to the way PCs functioned. While they were simplified for easy use, it was clear that a “mage” statblock represented a 9th-level wizard, for instance. They used the same spells and spell slots, and they had attack routines that usually made sense. This enabled us to have worlds where there isn’t a fictional divide between PCs and NPCs, and things like classes, spells, and even spell slots are part of the fiction of the world.
In the new version, that parity is destroyed. NPC spellcasters lack spell slots and have many of their combat spells replaced with unique abilities not available to PCs, and these pseudo-spells can’t even be counterspelled, among other more subtle changes.
In the old statblocks attack routines
usually matched character class expectations. So NPCs approximating character classes who get Extra Attack would get Multiattack, and those who approximated classes without Extra Attack wouldn‘t (except to approximate two-weapon fighting). Just like with spellcasting, you could look at the amount of Sneak Attack damage NPCs got and approximate an equivalent rogue level for them. There were a few exceptions with Multiattack, and they started popping up more in recent years, but that was the general design paradigm for most of the edition so far.
The new versions completely throw that paradigm away by giving multiple attacks to all sorts of NPCs that approximate PCs classes that don’t have anything like that. They also grant them superior abilities that PCs can’t even approach.
Here’s an example from an NPC from Wild Beyond the Witchlight that is (explicitly) supposed to approximate a mid-level sorcerer.
Multiattack. Kelek makes three attacks using Sorcerer’s Bolt, Staff of Striking, or a combination of them. He can replace one of the attacks with a use of Spellcasting.
Sorcerer’s Bolt. Melee or Ranged Spell Attack: +6 to hit, reach 5 ft. or range 60 ft., one target.
Hit: 13 (2d12) force damage.
Here we give a “sorcerer”
three attacks at-will, which can be melee, “cantrip” or actual spell.
The pseudo-cantrip option does force damage kind of like a shorter ranged
eldritch blast with a bigger damage die
. It is literally superior to any attack cantrip (it‘s actually scaled appropriately for this mid-level foe at two dice), and they can do it three times a round! Thats 6d12 force damage at-will, or 4d12 plus a spell.
And instead of
fireball they get a special “fiery explosion” attack that replicates a
fireball (with a 120’ rather than 150’ range) cast in a 5th-level slot, can’t be counterspelled, and can be cast an unlimited number of times on a 50% recharge.
As a player I would be like, what the crap? Why can‘t I cast three superior cantrips per round and fireball all day long?
As a DM and world-builder who liked the PC/NPC rough parity in 5.0e this statblock is completely unusable to me. I like the Wild Beyond the Witchlight adventure, but I have to redesign every NPC statblock in the book to use it, and all the monsters will get a close examination, whereas in the past I could just use the statblocks I paid for.
They could have easily made statblocks easier to use by printing simplified versions of spells and still using spell slots (the NPCs in Level Up shows an example of how that works), and no one would complain about that. Instead, they decided to make a hard shift towards a certain playstyle that prevents you from having a world where NPCs conceptually have classes, cast the same spells as PCs, etc. Now they force a world-playstyle where classes that function like the PHB with things like spell slots and clear Extra Attack patterns just represent the PC way of interacting with a much fuzzier fiction of the world, while NPCs use entirely different mechanics designed to give them much higher damage output than a PC can achieve.
During the 5e playtest, which well over 100k people participated and took surveys about, they explored the various ways of handling these things and based on the feedback created the 5.0e design paradigm, which was a great balance between the PC/NPC parity seen in most editions and the simplicity of using NPCs also seen in most editions (the two most recent previous editions each went extreme on one of those considerations and completely ignored the other, whereas most previous editions to them made a better harmonized balance). It basically worked fairly well for almost everyone and united the fan-base as designed. This new version of NPC statblocks picks one playstyle and world fiction to present and changes statblocks to be unusable to anyone who wants to play with a different way of looking at the D&D multiverse (which was the same way presented in almost every previous edition of the game). And as I explained above, this change was completely unneccessary. They can accomplish the same goals of DM accessibility without doing this with a few different design tweaks, instead of choosing to ignore the preferences and product needs of the people who participated in the playstest that made this the most popular version of the game ever.
Hopefully that helps explain why some people might prefer the older versions of the statblocks.