I thought the epilogue was supposed to be the Snapchat credits. If not, then what is the epilogue supposed to be?

We don’t know, but I mean, the story is still continuing. We still don’t know if our Caliborn and LE are the same, or if the Masterpiece Caliborn is an Alt Timeline Caliborn. John is depressed, Terezi is still searching for Vriska. There’s a giant hole through Paradox Space. Honestly some plot point like, Condy reviving could totally still happen and close off some of the last few loops here and there. Happy end for the ghosts perhaps? Earth-C Cherub Portal? There’s a ton of ways things could go still. Snapchat Updates are just Post-Canon Content, but not the Epilogue.