What people don't like the most is not AI being too difficult.
They don't like unfair things.
So creating really innovative, taking a ton of mind power and work to implement new AI levels, maybe totally pointless.
New player sees new units being produces en masse.
His natural justice system screams "unfair".
It's not only about unfairness, there is also a progress issue. Starting the game You are bombarded by a ton of new units You yourself cannot make - they are distant, alien and in many cases - completely out of place.
While progressing the game (getting gems) only player changes - AI stays the same. No matter the map there is always the same hard AI capable of everything. It becomes boring.
Easy campaigns are only easy when map creator made AI without any factories/TC or trigger changed production (there is no such case among easiest campaigns).
Challenges or historical battles could use few defined, limited AI types. Campaigns even more so.
Giving AI special disadvantages, especially when it needs code change every time seems like very inefficient way.
Especially when another solution lays around ( Collecting ideas
- last post).