There used to be a dozen sites like 4chan. I don't know if any of them are still around, but I'm willing to bet that if 4chan doesn't come back there will be a new website that takes its place.
4chan is a pretty unique experience. Most of the internet is forming into echo chambers, where having a different opinion than the "correct" opinion for that community will get you downvoted or banned. My understanding with 4chan is that post popularity is determined by replies, and frequently controversial opinions/etc get the most replies. So posting stuff that most people will agree will result in a less popular thread than posting something controversial, offensive, or wrong.
I think this leads to a lot of the negative things you've heard about 4chan, but encouraging disagreements between its members keeps it from becoming a full echo chamber like a lot of social media. They still have some dominant community opinions, but those opinions can't really smother all the other opinions like on most sites.
To be clear, 4chan is a cesspool. But for all it's flaws it does offer something unique that's largely missing on other websites.