oldfag here (used 4chan in 2003-2004 although i'm not proud of this)
let me tell you how old /b/ was.
1. anime, longcat, YLYL, milhouse is a forced meme
2. "why don't you have a girlfriend, anon? you're almost out of college", with a porn pic
3. a nerd faggot would make a single post, e.g., about something like his purchase of some gay shit for World of Warcraft, and a "bully" would reply
>you sound like a total loser with brown stains in his underwear
and be right. and the nerd would be BTFO and become incredibly paranoid after learning that someone knows the state of his underwear just from one post he made
soyjak is the same thing: it's used in response to a common type of retard who is so predictable and common that you could tell how he looks just by seeing a sentence he typed
the meta has shifted slightly but it's basically the same: some whiny faggot would explain why women should be forced to marry him. then a "bully" would just post soyjak, implying that even if he isn't an SJW like soyjak, he still reasons like one. there is even chudjak and muricajak for this
if you're screech over soyjak, suck mod dick, or cry that your oh so important thread was derailed, all while pretending to be an oldfag, you're cringe. recede.