I agree. Space victory is my favorite victory condition, and I tried my hardest to win by science in my last game, but ended up winning diplomatic by accident.
While I certainly can't say I won my last game "by accident" (I was making sure to keep or grab city-states, and ensuring that proposals favouring me were passed), I have now found several times that diplo victory can just come too early on smaller maps (when it's quick for half the civs to reach the Modern Era). I was making very good progress towards a science victory on Immortal, but ended up having 22 votes for World Leader (needing 20 to win) before I'd reached Particle Physics. I could always have refrained from voting for myself with all my votes, I suppose (I don't like the fact that the spaceship is disabled after you win, so you can't carry on to build it with Just One More Turn).
While I think there probably is an issue with the diplo victory being too easy on certain map sizes or without civs that actively compete for city-states, I still don't recognise the gold-farming description. In that whole game I spent money on CSes perhaps three times at most, and not one of those purchases caused me to become allied with that CS (even the one I paid 1,000 gold while it had a gold quest underway). Since I won with two votes to spare, even the extra influence towards alliance (which I did eventually achieve) with that CS wasn't game-changing.
My victory might have been too easy, but it did require me to actively play for CS favour and delegates - I needed to get Forbidden Palace, I proposed (and won) the International Games for the boost in CS influence, I proposed (and secured) a World Ideology, I took Patronage and Papal Primacy, I had to focus on both science and faith to meet periodic quest requirements, my spies were on full-time election-rigging duty and in one case orchestrated a successful coup. It was very far from an economic victory (although I did capture Cahokia with a Merchant of Venice Zanzibar kindly gave me just in time to buy the CS before the final leader vote).
I never really understood the whole concept anyways. I buy enough city states to get just over half of the "world leader" vote, and the 45% who voted against me just acquiesce and accept my sovereignty over their empires? Even if they hate me? I might just disable it from now on. It makes sense to have an economic-based victory condition, but the premise behind the current Diplomatic Victory is just strange, and I don't like that I can accidentally trigger it just by having a decent economy and wanting some influence in the World Congress.
None of the victory conditions make any sense in that context. Everyone bows down before you when you have all of their capitals, even though all the surviving civs hate you? You win a space race and suddenly you're the world's greatest leader (even in cases where, as in one of my games, my capital was a turn from being captured when the spaceship launched - more a desperate exodus than a great triumph of world civilization) etc.
I will repeat my previous point. At the end of the day, the current system of "buying" City State Influence is extremely *game-y* & doesn't reward skill or good game-play. I'm not saying that influence buying should be entirely removed, but it should be the "option of last resort"-usually garnering a very small "benefit to cost" ratio, unless said City-State is seeking investors. The bulk of all influence should come from City-State Quests, Trade, Use of Spies
Which exactly matches my experience of the way it does work.