If AI really was such a game-changer, it would increase the chances of finding extraterrestrial aliens, not decrease it. If AI allows for superhuman feats of intellect and engineering, then even if 99.9% of all strong AI leads to the destruction of the original civilization, you'd only need the 0.1% of civilizations that develop stable benevolent civilization-boosting AI (let's call them The Culture). Those would spread around, and we would have seen them. So we're back at Fermi's paradox.