So you are saying there is a line somewhere and judgement is needed to decide what should be reprinted verbatim... NPCs with the spell casting ability will just have a list of spells. I don't see how that's unreasonable.
Let's say they publish an adventure module where the players have to fight a bunch of sickly, elderly acolytes of the God of Lightning. These priests have no interesting powers to speak of and are too weak to even lift a sword and have no melee or ranged attack, however because of their limited priestly devotion they can cast two spells (and that's it): Lightning Bolt and Cure Wounds. The spells are the ONLY interesting thing about these enemies, and there's only 2 spells. I would argue it is very unreasonable to not print at least a summary of those spells in the stat block, as it already takes up so little space, and you're basically guaranteed to have to look the spells up (or play the enemies VASTLY different from how they are intended).
In general, I don't see any reason for a blanket rule of 'we won't print any spells'. I think spells that will need to be quickly referenced in a fast-paced/tense scenario such as combat/sneaking/social interaction should be handy and not cause a break in play by forcing a rules look-up. Extrapolating that reasoning to a more realistic example: say there's a powerful demon that can cast Fireball, Detect Invisibility, Suggestion, Divination, and Control Weather - I would propose that a summary should be provided for Fireball, Detect Invisibility, and Suggestion. Divination and Control Weather could simply be listed in a line as 'See Spell Description: Divination, Control Weather', as those are relevant to the creature's back story and away-from-immediate-action impact on the game, but unlikely to be relevant in a tense, time-sensitive scenario. These are the judgment calls I'd like the designers to make, but they are not doing so with the blanket rule of 'no spell descriptions'
I agree with this. And as Merric pointed out, it sounds like Mike Mearls agrees with this...except for spell casters
Mearls' quote is actually encouraging, and it's good to know they recognize the importance of making core monsters easy to play. If you're going to have spell lists, there are at least ways to alleviate the issues they cause, and at least they seem to be taking these steps. I just don't get why they need to handcuff themselves with a blanket rule about no spell descriptions.
but sometimes you want a monster to be a spell caster and have all the flexibility that infers... Look at a the 4e Lich... But it doesn't feel like a spell caster to me. I want my liches to have the same flexibility as a PC wizard and generally follow the same rules...
And I would never want to take that away from you. I'm just arguing that a monster such as that should be in an 'Advanced' Monster Manual, so as not to be a land-mine waiting to trip up a new DM (or a rules-light DM), who's just trying to quickly snap through an encounter with a spell-casting creature, and doesn't want to get caught having to look up a ton of rules (or play the creature ineffectively).