Some things to keep in mind:
The term “AI” in Unity ONLY refers to the 3D-only Navigation portion of the engine.
The Navigation system is only useful for going places that can be gone to.
There is no “AI” per se. You would be responsible for coding the intelligence of any given agent, including agents using the Navigation system.
This is the equivalent Navigation system for 2D: 2D NavMesh Plus - Components and Extensions System
The Navigation system DOES NOT in any way change behaviors or “intelligence” of objects.
There may be other 2D Navigation systems you can purchase on the asset store.
As an aside, there is also no Unity2D. Unity3D can display 2D objects but it is still Unity3D.