Agents are very powerful if you know how to use them, dignitaries easily boost your income by a huge amount in early game and they can convert culture pretty fast, reducing chance of rebellion
spies are very good at scouting, poisoning armies
champions are pretty much the most powerful agent, they can completely devastate a settlement in 1 turn, train your armies into extremely elite units
in Legendary they help me so much, I always recruit dignitaries first and let champions be full slots all the time
and the AI? well they are pretty annoying but it's fine, nothing should be changed
dont blame CA for something like this, it makes you look even more noob (sorry, harsh but true)