If I had to guess one thing most players do that would hold them back, it'd be that they upgrade all their buildings. Don't upgrade your buildings unless you are certain they can service at least 3 or 4 houses efficiently (very close with good happiness). Lumber mills in the midst of a lot of forest are often good candidates. I've gotten to the point where I think its only good to create one ginormous granary in order to get one food house very high and hope to lure in some dowries in addition to the extra production it gives you.
Rather, build more small buildings that maximize efficiency (adjacent to the resource and a house which has at least a couple happiness sources) and save all that excess production for troops. That is the path to domination. Build up your stacks of 100's of troops while the people you fight that are busy upgrading every little building throw up much smaller ones because they have very little production left.
Obviously a university should always be upgraded, but the one above is not ideally positioned. He did it because he must have created a ginormous library before village green was available, then built a ginormous village green, and then replaced the library with a university because he didn't want to move the village green or build another. But you should want to build your university in a spot where you have space on all sides (with a ring of forest/water around), and here the palace is eating up a quarter of the territory. I've gotten to the point where I often won't even bother building a library for precisely that reason, cause I'd rather just wait til code of laws / university are available and find the most ideal location.