LOL that is really disappointing, thanks. Did you do the post dungeon or whatever?
Without spoiling anything I'd say I'm about 3/4 through the meat of the postgame.
There's actually very little of the postgame that is mandatory, and I've had access to the postgame final boss for a while, but I'm doing a complete sweep of the overworld and doing any and all event-related postgame stuff (of which there is a ton) before I give the final boss a go.