A Boring Dystopia

Typically, your claim will be reviewed by someone with no medical history, they are just an insurance claims agent. They don't have to have any experience or any particular education beyond high school. This person will require copious amounts of medical documentation from you. Both documentation from all of your doctors' offices as well as long forms for you to fill out. Obviously, this is never a massive burden for the disabled (/s). If it's Cigna, they will likely lie and say they didn't get it and you'll have to send it all over again. This will go on for multiple requests. Great delaying tactic!

After they "review" and deny you, which they will, it goes to a physician paid by the insurance company for approval of the insurance agent's opinion. If the agent denied your claim, the doctor is not going to disagree. They will deny your claim "medically". On the extremely off chance that you were approved on the first round, which, let's be honest, you weren't, the doctor will try to find a way to disqualify you. They are paid specifically to find reasons that someone doesn't qualify. And that applies to both the agents and the doctors. Sometimes nurses are in there as well. Sometimes insurance companies will try to have nurses make the decision instead of doctors and you have to insist on a doctor.

Once you know a doctor is looking at your claim (or has auto-denied it, as their managers expect), and especially after it has been denied (which of course it has been), you need to get what's called a peer-to-peer call between that insurance doctor and your real doctor who isn't just some corporate shill. Your doctor will schedule and handle this, but you will have to ask them to do so.

Then your doctor explains why they are wrong and you get approved. Or you go through a back and forth for a while and hope for the best.

Signed,
Extremely familiar with the process and not at all bitter

Edit: This is how Cigna's disability process works. It will be similar but with fewer steps and people involved for regular insurance claims like getting a test paid for.

In both cases, the process is deliberately designed to confuse and exhaust the patient so that the insurer doesn't have to pay out. It works a lot of the time.