I'd go with a more recent classic from Age of Empires, the monk and its "wololo" ability to convert enemies to become your unit. To keep it balanced, maybe it should only be able to convert certain pieces and taking more than 2 turns to complete its conversion as to give the opponent a chance to counter its special move.
EDIT: Totally off topic,but..
I just found out that if you put an evoker in minecraft next to a blue sheep, it'll do the wololo sound and convert it to a red sheep.
If you're asking it to add numbers below 10 there's an up to 5% of getting it right. And I doubt you're asking it to add 9+9 so probably closer to 10% and above if you're asking it to put, say, 4+4 together.
That said, I don't think they're dumb at all.
Out of animals their size, they've found a niche for sure and avoided becoming irrelevant for thousands of years (since ~3500 BCE).