Frequently randomizing tile yields would reduce micromanagement? Not at all. Quite the opposite: players who value efficiency would be forced to micromanage citizen assignments on every city every time the "season" changes and the yields change. No problem for the AI, but hell for the player. As for randomizing Eurekas, it's an example of a realistic stance taken for realism's sake, without any consideration for actual fun. Eurekas are an interesting mechanic that give players mini-objectives in order to get a reward. All that would be lost if they simply became random. Sure, the AI wouldn't have trouble with them, but randomness won't reasonably solve AI problems. Might as well make combat damage random and load the dice in the AI's favour: boom, 1UPT "solved".