I feel sort of sick remembering one meeting where they told us our daughter would get 24 hour nursing care covered by insurance if we got her a tracheotomy, what a weird carrot to dangle in front of a parent. I think they thought what they were suggesting was the best medical choice but a baby with a trach needs 24-hour care because it can’t even cry when the tube is in its throat.
Luckily I'm obstinate and finally saw a specialist who correctly identified it and treated it, but it's critically important to be very active in your own medical treatment. Get second (and third, and fourth..) opinions, raise lots of questions, push back (politely) against things that don't seem to make sense.
I would alter this slightly to "have a trusted advocate do research and talk to many doctors". The person with the life threatening diagnosis may not be in the right frame of mind to advocate for the best treatment. Should you ever find yourself in the hospital, having a capable ally alongside you can make a world of difference.
When my mom was diagnosed with breast cancer my dad poured over literally hundreds of medical papers to determine the best course of action. I believe he saved her life. Scihub was instrumental in that. I helped a little in checking and challenging his conclusions. I think it's unlikely she would have had as good an outcome if we'd just listened to the doctors.
My conclusion is if you want the best medical care be sure to do your own research and talk to many doctors about your findings and treatment options. Do not blindly trust the medical community. They are years behind the current state of knowledge in their field and just do not have the time and energy to spend per patient to get the best outcome.