From the description of the mod I posted earlier in this thread concerning the Monopolies and Corporations mode fix:I always play with monopolies mode on, and in some game it did happen that the AI barely improve luxuries, but then again they settle like idiots most of the time. Last game they started to improving luxuries from renaissance era onwards. So my conclusion is that they do improve luxuries almost every game, even if later than me, but then again I make that a top priority on my every game!
This mod fixes the luxury improvement issue the AI has with the Monopolies and Corporations Game Mode by moving corporations to currency. I noticed that the AI worked correctly when you reached economics, so tested moving the requirements for corporation to pottery and AI went on improving everything normally. I decided to move it to Currency as it wont have a lot of effect on the game, as you need a great merchant to create a corporation anyway, and it turns out even if you have one it does restrict the creating until you actually reach economics. So fix works great.