TBH I don't get what this thread is all about. You all want to change some mechanic (and even able to provide specific numbers how to do it, which truly amazes me), based on single gameplay? I mean, really?
1. If the issue is year when players reach certain eras, then I have to admit I am little biased because I just don't care. But even if I did - is this new? AFAIK science victories were common under 250/300 turns in Civ5 (and possible under turn 200), and as I just checked, Quill is at turn 311 in his current gameplay and did not win so far (I have no idea how close he is). So, is there different ratio between turns and years as was in Civ5? If not, what's the deal?
2. To partly answer my question (I did not see any late game, including Quill's), it seems that part of the problem is that he has science tree fully researched, but it will take some time to actually win science victory, since it takes lot of production to execute it. If that is the case, it just mean that they have change a design a little bit, and in Civ6 you actually WILL progress a little faster through science tree, but you WILL NOT win SV victory sooner. That's not bad, that is just different design. So what you need to do, is change priorities and take more care about culture (which I guess has some policies to speed up Mars mission) and production. That will result in slower science and you all might be happy.
3. To me it also means that he is playing the game bad, by prioritizing science too much over other things. I didn't see his gameplay, but maybe he just builds many Campuses, which is just bad in Civ6 and he doesn't know it. And weren't these things common in previous iterations too? I never really cared, but I am pretty sure you could get artilleries in some totally unrealistic turn/year in Civ5 if you beelined it and didn't care about anything else, but a) that year/turn didn't matter and b) it wasn't a good path to victory.
4. Last but not least, you are really overestimating Quill's game. I randomly compared him and Marb in turn 193 (end of Marbozir's part 11). Science/culture Quill 127/56, Marbozir 71/59. I have no clue what's the reason, but I am pretty sure this thread wouldn't exist if we all watched just Marbozir (who I consider better). So, why don't we just give it a shot, and judge later?