I wonder how many people just find a different job during the wait and tell them to fuck off when they finally come calling, because it’s not like they give you updates and most people don’t really want to make a decades-long career out of it.

A lot. It's one of the biggest issues with recruitment. You think about your average 18 year old picking the military as their career; by the time they get told they can swear their oath and head off to St Jean, they're 20, probably have a girlfriend, a job that they've been at for a year or more, if they're really lucky maybe even the prospect of promotion or perhaps an apprenticeship that they're working on. Suddenly the idea of packing up your life to spend two months in basic, then sit around waiting for anything from months to years for your occupational training, before you can finally start a career really doesn't seem all that appealing.

To give an idea of how bad the problem is, when they opened up recruitment to permanent residents (a smart move, no argument there), they got 20,000 applications right away. Two years later, they had recruited 77 of those applicants. That is fucking dire. As a result of that they've reconfigured how they process security clearances, which will help some, but as you noted the medical stuff is a huge hold-up and there's no excuse for it. The entire medical review process needs to be completely overhauled. It should not take as long as it does to clear someone.