In my most recent game (I was Carthage), I choose fealty and still was able to win a diplomatic victory. I allied one CS (a neighbor) and traded with him all game, but totally ignored all other city states. I took freedom's policy for 10 influence per great person, which immediately gave me friends with everyone and eventually allies with most. Then I just dedicated two spies towards coups, this along with random quest completion allowed me to eventually swing every city state to my control. I only used diplomatic units in 4 city states throughout the game.
Freedom's influence tools were more than enough to uproot the statecraft empires' grip on city states. I looked back and didn't see anything in statecraft that I really missed. The massive faith discounts and direct faith generation of fealty enabled me to eventually convert all civs without religions to mine, and eventually swing a founder to my religion as well. In my experience is by far the easiest way to gain WC control is passing world religion on the first session, and I think fealty helps to do this more than statecraft does.
I haven't used statecraft very much in a long time, so perhaps people with more experience can offer better suggestions than I can, but I really think it needs some per city yields. Fealty and even artistry just directly provide more yields and yields win games. Trade route bonuses are interesting and thematic, however the number of trade routes doesn't scale with city number. Furthermore, you compete with Fealty generating 5 gold per city from its scaler alone. There was not a single time that game where I looked back and wished I had statecraft instead.
The current opener is awkward. Its worth about 1 yield for every 4 citizens, which is is better than it sounds but its still crap compared to monasteries. 25 is a really large number, you lose a lot of yields due to rounding