I agree, that is crazy long. The ophthalmologist MD office I go to is a mad house. In one room, wait, into another, wait. At the end, see the MD.
I agree, if they were that behind, calling people and cancelling/rescheduling non emergent appointments would be the best. However, if someone had an emergency and it was myself with the emergency, I'd be grateful for the immediate care.
When I had the carpel tunnel surgery, I showed up and they had me come back later. The surgeon had an emergency. Someone had broke their arm falling off a ladder. They had tried to call but I had already left since I show up early for stuff like that.