Most people aren't that interested in complete manual control over their Polaroids. Which is totally understandable, instant prints should be taken instantly without hesitation
The problem with cameras 30yrs old, or more, is that they typically arrive in poor shape. Usually the battery compartment is corroded and dust has found its way into all the tiny places within the camera body. Sometimes, the shutter is broken or not correct. All the glass/plastic lenses are probably dirty as well.
The most frustrating part about pack film bellows cameras of the 60s and 70s, except for a few models, is that they take either 3v or 4.5v batteries. Most likely, you can not find these batteries in your local store, and prices online aren't so cheap. The best way to keep your camera in working condition, is to modify it to take easily obtained batteries.
Because the battery mod involves opening and cleaning part of the camera, it is a great opportunity to clean everything and also check the shutter circuits, among other things.
So while this reconditioning is focusing on the 100, the process should be basically the same for any other model which also takes 4.5v batteries. Typically the models which have a "scene selector" require 4.5v whereas the simpler shutters with only a film speed selection are not.