Is a lich (monster) counted as a spellcaster for attunement?

DMG chapter 7:

Attunement Prerequisites. If a magic item has a class prerequisite, a creature must be a member of that class to attune to the item. If a creature must be a spellcaster to attune to an item, the creature qualifies if it can cast at least one spell using its traits or features, not by using a magic item or the like.

The way I understand this is that they were basically trying to say that a spellcaster is either a player character with the Spellcasting or Pact Magic class feature, or an npc with the Spellcasting trait.

As we all know, Spellcasting trait no longer exists in Monster Manual 2025 anymore, it instead is defined as an Action a monster can take, rather than a trait or a feature, like how you wouldn't call the Attack action a trait or a feature.
So by RAW a lich cannot attune to a Wand of Web? 

Am I missing anything here?

Quote from Scichopath >>

 

As we all know, Spellcasting trait no longer exists in Monster Manual 2025 anymore, it instead is defined as an Action a monster can take, rather than a trait or a feature, like how you wouldn't call the Attack action a trait or a feature.

There are plenty of monsters in the new Monster Manual that have a Spellcasting ability, including the Lich. It seems highly unlikely that the fact that it's listed as an "action" rather than a "trait" is meant to have any mechanical impact on what items the thing can attune to.

Regardless, it's probably a mistake to try to strictly apply to monsters any rules that are intended for player characters. If you're the DM, and you want a Lich to be able to use a wand of web, then it can use a wand of web. That's your call. 

Mostly what they're saying is that a PC needs to meet those requirements to attune. NPCs can attune whatever the DM says they can attune.

Quote from Scichopath >>

 [...] As we all know, Spellcasting trait no longer exists in Monster Manual 2025 anymore, it instead is defined as an Action a monster can take, rather than a trait or a feature, like how you wouldn't call the Attack action a trait or a feature. [...]

 This is right. Spellcasting, for monsters, isn't a feature or a trait. It's just an action they can take. If you're interested, it was discussed in Does Shapechange Retain Your Spellcasting or the Monster's? 

In any case, I agree that the Attunement Prerequisites rules are written with player characters in mind.

I know when it's about monsters everything is the DM's call ultimately, but it becomes a problem when a monster is players' resource. For example, can an imp familiar use a Wand of Web? The rules are not clearly written, I am just annoyed to see little problems here and there.

Quote from Scichopath >>

I know when it's about monsters everything is the DM's call ultimately, but it becomes a problem when a monster is players' resource. For example, can an imp familiar use a Wand of Web? The rules are not clearly written, I am just annoyed to see little problems here and there.

 It would be useful to have rules for minion attunement. My general thought on that is that familiars and the like use their master's attunement slots, which greatly limits the potential for shenanigans, but that has more to do with dislike of minion swarm builds than any RAW support.

D&D is an asymmetric game, so "rules for me and not for thee" isn't an inherently valid argument against a DM's call. Attunement as a game mechanic largely exists to cap player power, along with easing play by limiting the amount of moving parts on a sheet a player needs to track. A DM does not need to justify why an enemy monster can attune while a player's familiar can't with more than "because I wanted to add to the stat block for the encounter".