This a thousand times. My last game was a blatant, shameless copy of Tabarnak's game which he posted on this thread. Now the differences were that i didn't have 1 city with a river(4cities), and i was also forced to delay the last city due to mistakes(not hooking up the luxuries in time), i also only had 3 unique luxuries, biggest plus for me was the fact that i was fairly isolated and had lots and lots of copper around if i only had ppl to trade with, China who had the biggest wallet the entire game hated me 95% of the game, we were at war when i was building the UP.
In addition, i had a very hard time accumulating wealth, when i saw the screenies of Tabarnak i can see that he was making at least 4 times the money during a GA than i during the same turns(techwise i was pretty close to him i think). I'm not sure where such huge differences came from, but i suspect city pop may have played a role here.
I got one GS from the capital, missed the other one cause i decided to delay the GS for city growth which was a big mistake(i wonder how many GSs Tabarnak eventually accumulated).
There were 5 cultural CSs, i never met 1 CS, but i guess the probability of that CS being a cultural would have been slim. Anyway i got two of them from the get go. The last three were incredibly hard to get on my side, even if i bribed them with huge sums. Theodora would coup in 1 turn and make all my spent gold worthless, happened at least 3 times(this coup mechanic is broken).
I was forced to send my spies away from the

CSs i currently had and make them work my prestige up in these others cities, which took an eternity.
Eventually i had them all at my side, but the difference was marginal - the last city was couped/bribed somewhere b4 the last 10-7 turns of the last policy.
Most of the policies game at 5-6 turns, after about 200 turns once the permanent GA started, possibly even earlier. I settled a total of 8 GA's - now here's where the river could've helped. The last policy came in 7 turns while i was producing a whopping 1196 culture per turn(but this is with Siam ofc). I think i teched CR at 242, but not entirely sure about that anymore.
Despite all of these problems i understood somewhere at middle game that if i don't mess this up i will finish with my best time(eventually at turn 278). That is 20 turns better than the previous best time i had, Utopia took 9-10 turns once the micromanagement of tiles and railroad bonus kicked in. Citygrowth is integral for a fast finish, you need it for science/gold/hammers/culture and the cities have to be decent productionwise, cause you'll want a wonder in each of them for the piety bonus.