People aren't thinking the UA through.
IT's not that overpowered, it just sounds, why? Because fo this :
It cleary states that you "steal", meaning that you can't gain techs that YOU don't have.
You can only gain new techs from civs that are more advanced than you.
This means that Civs which are technologically davanced will still own you with their superior technology.
So in order to use the UA you need to be lucky and smart enough to take a city without being overrun by the AI first.
But you don't even need to build university in every cities to reasearch a techs!And your target is very simple:who is the first of technology.If the UA let you get tech immedately once you capture enemy city,one city equal to one tech,may including the science buildings in the cities you capturing.That's too imbalance!If the UA acts really as the spy stealing tech,which means you need turns and face risks to get them,the UA will become a great fuuny strategy to play and decide.If not,that just call you to build as many military units as you can.