Agendas were very meagre and low effort replacement of personality flavor scores. Flavor scores with variety margins ensured very distinctive and not quite the same leader personalities from game to game in Civ 4&5. But in 6, on the one hand devs went out of their way creating unique aspects of different civs, on the other hand they spared a lot of code to ensure that AI leaders could truly utilize them.
Agendas, at least, could have been a gradually evolving thing, adding something with every passing era, they could have been organized a bit like policy trees of Civ V, with diverging paths for different priorities, to bring some variety from game to game.
And surely there had to be some code for the AI there, to back their blabber. My coast all too easy to raid, you say, Harald? So what will you do about it, will you come and raid? No, I did not think so. Lost all your longships to barbs, what a shame.
And, on the same note, slapping campus and theater districts as priority ones for all the civs across the board in one of the latest patches, thus making all the civs even more alike among themselves, is just full capitulation from the side of the devs. No time and resources to make a proper job, but here's some magic bandaid for quick application, should work wonders. Except it doesn't.