It has been odd, to say the least.
I went to 4chan when I was 21, back in 2005. I found it hilarious, at a level I had barely seen before. The memes were slightly more original, and every day there was more than enough pictures that I had never seen before. Of course people were edgy and try-too-hard back then, but there was no standard for that and as such people acted like real people.
I was never one of the crowd. I usually just stuck to /d/ because I liked seeing anime girls getting milked or fucked by animals. In 2008, /jp/ showed up, and I joined it a few months later. I never even went to /a/; /jp/ was just really interesting for me because we were all just a bunch of alienated losers who talked about staying in their rooms and enjoying solitary activities, like collecting dolls, playing Yume Nikki, and trying to create shit. It was the first time I ever even halfway fit in somewhere. It introduced me to so many awesome things, like Touhou, Elona, traps, and eventually SSI and being a perma-NEET.
I didn't even watch anime (haven't for over ten years). I just loved being there, with people who were even slightly similar to me. I still read manga occasionally, though.
But 4chan was only one place that I went to; in many ways I preferred Pixiv and later on 420chan. I did get into some of the culture, in that I liked talking to shemales and cross-dressers back when it was popular, and started taking OTC medications to get high when that took off, but for the most part I belonged to no one besides myself.
I stopped going to 4chan in 2013 for many reasons. I was getting older, I didn't fit in anymore, nothing was original there, few things were funny, /jp/ wasn't interesting anymore, I could find my porn somewhere else...the list goes on. But I think what stopped it is that I simply found better sites, such as this place and 420chan.
To me, it died before most people said that it did. I wouldn't ever go there anymore, because I despise how m00t betrayed everyone just to get some SJW pussy (who ended up cucking him) and to obtain more Jew gold. None of that is worth my time; I have all the time in the world and none of that is worth a second of it. I'd much rather make my own imageboard and just 'tard off there; I could, 8chan allows that.