I've definitely seen countless examples of passive AI ever since Immortal empire release. It's as if CA got too much backlash in version 1.0 for AI being too aggressive and just nerfed it to the ground.

Here's an example that I've seen many times with crisis factions. Been at war with them since turn 10 and I got sight of this since at least 20 turns.

Not only Legendary difficulty, other difficulties too! I encountered on hard mode!

beware if you are using some AI mod

and exemple, organic AI remove the threat from the player to AI instead of tuning it. Probably because the author didn't take the time to read how is calculated threat

It's probably the case for some others ai mod

Thought I'd give another example from Very Hard. Valkia the Bloody is just standing there with stacks of 1 or 2 unit armies doing nothing.

This is so frustrating that this hasn't been addressed yet in the latest patch.  How long is this going to go on?  It just kills the game when the AI just sits passively in one spot.

It's not just the sack-and-run issue either.

Even factions with Legendary Lords, like Sigvald's faction, can sit for 50+ turns literally not at war with a single other faction.

Back in the days of Total Warhammer I, Wood Elves were known as the one faction that plays excessively passively and holds its Athel Loren territory, to the point of not declaring war on anyone for lengthy periods of time.

Now, even anti-order factions and all sorts of other factions that are not Wood Elves sit around literally idle.

So we went from one terrible campaign map gameplay setup, where factions would declare war on the player from the other side of the Immortal Empires map without every being in contact with the player... to a map full of mentally addled factions that either declare war and just never finish off their enemy, or just don't declare any wars ever, and stack five armies around their capital forever.

Kholek stand with 3  full army next to enemy setlement and doesn't attack and Nakai just stant with full army near his starting location.