I think people are underselling the yields from TtGoG a little bit, at least if you managed to convert someone. If you can maintain the full 20 cities (call it two 8 city empires and four CS), thats 60
for every GP. Assuming you have like, maybe 8 Amphitheaters with FoTM, that's 16
in bonus yields. If we call
worth about as much as
, especially on this new spy system, and
worth maybe a quarter as much, that's equivalent to ~135
. So if you pop a GP every 8 turns or so that equalizes the yields until Opera Houses. That's more than a little optimistic, but even getting them less quickly or with less cities will really cut at the early advantage some of these other beliefs can give.
And later on, in Industrial, well those yields aren't that hot anymore but you are getting them once per five turns like clockwork in addition to the normal triggers. And basically any civ is going to be able to either get Great Writers or Great Generals they don't deserve, in addition to either Great Artists or Great Diplomats they don't deserve (the Diplomats are still usually useful for embassies at the very start of Industrial in my games.) Like, I know stuff on delay is bad, but 2+ each of a bunch of different GP is just a very lot.