>>320579/pol/ and the 2016 election, I'd say.
Not that things were all rosey before that, but this was the time when this site became known to everybody, and every edgy kid on the block decided to come here to get its edgy maymays.
From this chart, I'm theoretically from Reddit, but I'm not. I'm not usually against those who have been on reddit as long as they follow the rules of this place and behave like they're expected.
But this election in 2016 was the ultimate death of this place: you just have to see the massive spike in popularity of the site to get an idea of that.
/pol/ attracted hundreds of thousands, to the point it surpassed /b/ by a long stretch, and this cancer is spreading to other boards with an increase in the number of low-level race-related threads (such threads existed before, but they were of higher quality for sure).
Only a few obscure boards are somewhat safe from this onslaught, but it perturbed the ecosystem of this place to the point of destruction: board culture is gone, intelligent discussions are gone. Not to say that banter and shitpost wasn't a thing, of course it was, but you simply can't have a serious discussion anymore on this place...
I had high hopes for this place when I first discovered it: I hoped to find people to discuss with, people that could share my view or instead debate it correctly, to make me greater and happier. But it all ended up with a flood of pepes and natsoc retards...
Now there's nowhere else to go, and I feel all the lonelier.