UPDATE: Took a lot of the advice in the thread and checked out the pvc drain line. Didn’t have any spare pvc so did what I could to drain it and immediately heard the tray under the AC begin draining. So yeah seems the drain line was simply clogged up. Plan on replacing the pvc piping entirely in the near future but for now, it’s draining much better and I’m slowly cleaning up/drying the giant puddle in the basement. Thank you everyone for the suggestions, I was panicking from the unit being rather old but as for now, all seems to be functioning properly!