Took a look at the save. Short answer is that you've finished schools, so you are at the traditional point of saving GSs to bulb later, but you aren't on a path to generate many GSs (you're only generating 9 science GP points and your next GS won't come for 21 turns).
You're at turn 288 (epic speed) on a large map, Emperor difficulty, full Tradition and left side of Rationalism to Free Thought, so I'm assuming you are aiming for a Science VC. Your beakers roughly equal the turn count (284 bpt), and I don't know whether that is good or bad at epic speed (I play standard). BUT, you aren't working your university and school specialist slots right now -- just working the specialists will take you to 327 bpt and boost your science GP points to 29, delivering a new GS in 7 turns. And you have no TPs - spamming out some TPs would seem in order.
One of your academies came from the PT GS, and you bought 1 GS with faith [EDIT: I forgot about the epic modifier - you had not bought a GS with faith yet]. Where did the other 2 academies come from? Did you take a GE at Pisa to slingshot PT, or did you spawn a GS there as well and hard-build PT? I'm guessing you got at least one GS from passive scientist points generated by the Great Library and Oracle.
You are building Taj Mahal, which is nice, but it's not like you've switched to production focus and inadvertently lost the specialist assignments -- you're on default focus, which means you may never have been working the specialist slots. You do need to grow your capital as aggressively as possible, while working the specialist slots. You are generating plenty of food (next citizen in 9 turns) and Taj is done in 4 turns, but you need to get those specialist slots filled ASAP. If you assign the specialists, lock down the academy tiles and best food tiles, and stay on production focus, food surplus falls only a slight bit (next citizen in 10 turns) and Taj stays at 4 turns. You also need to friend several maritime CSs. You are about to win a faith quest from Cape Town, which will be a great benefit. I would drop 500 gold on them now to get just shy of friend status, and lock in a lengthy friend period after the faith quest. You can also drop 1000 gold on Mombasa to get about 35 turns of friendship (that 2 food gets your time to next citizen back down to 9 turns). Getting an additional 4 food in your capital (before Tradition and religion bonuses, and the WLKD multiplier--you need to get furs somehow to kick off a WLKD) can be very useful.
I assume you took Oxford to get Astronomy and into the Renaissance. But, your current tech order would take you from Industrialization through Navigation to Archaeology -- why? You do not want to be generating Great Artists (they just eat into your GS capacity) and should be beelining Plastics at this point. You are 7 techs away from Plastics, with 2 RAs - one with Ramy maturing in 13 turns and another with Alex that you just entered into (Alex is still in Renaissance and you had to pay him for an RA; Austria would have been a better choice - she's also in the industrial and apparently only unwilling to friend you because you friended Alex).
In short, work the specialists, beeline plastics, rush buy a lab with gold, and work that specialist slot as well. Then beeline to Satellites for Hubble for two more GSs. Your next social policy comes in 20 turns, but you need to build more culture buildings (move Hermitage up in your build order) and friend some cultural CSs (you are getting no CS culture). Milan has asked for pledge to protect and is offering gold discounts (500 gold and a pledge will get you about 50 turns of friendship, for 13 culture per turn, shortening your time to next policy by 6 turns).
Dropping most of your gold on CSs will also allow you to make peace with Sejong for 17 gold. You don't need that distraction.
Since you aren't doing that many RAs, you might consider a detour to Order and Planned Economy for a cheap factory, 25% science boost and the ability to buy a GE for Hubble, before finishing Rationalism (as is, you may finish Rationalism too soon to take best advantage of the two free techs).
Attached is a save file that makes the changes I suggest (still turn 288).
EDIT: I went ahead and finished my version of your save while watching the college football morning pre-game shows (lots of "Next turn" in an OCC game). I take back what I said about it being time at turn 288 to start saving GSs for later bulbing. You were much further behind than I realized (I have no feel for epic timings). Should have planted more academies, and gone for diplo victory -- would have been MUCH faster. I launched on turn 504, which seems woefuly slow even for epic.
I did have one bit of real fun. For my last naturally spawning GS, I timed everything to generate a Great Artist, Great Engineer and Great Merchant on the same turn. First time I've ever spawned 4 natural Great Persons on the same turn (done 3 at a time several times, and two at a time many times, but 4 was a bit tricky).
