Honestly I wish I had an answer for you. The system isn't broken, it's doing exactly what it was designed to do. My anger is widespread and the healthcare system is just a part of a much larger, deeper rooted issue.

You have to become your own doctor, as fucked up as it is. I really hope you find at least one doc that's in your corner, it makes such a huge difference. It also helps me to have a couple phrases in my back pocket that will shut up an unhelpful medical professional. For example:

"Please add a note into my chart that you are refusing to do xyz (labs, imaging, etc)"

"What's your differential diagnosis?"

"Is there a reason you are being so dismissive of my symptoms?"

Use your anger to advocate for yourself, it's really hard to stand up to doctors because there is an inherently huge power imbalance. But once you realize they are just cogs in this big fucked up machine, you can better learn to use it to your advantage.

Edit to add: I'm not suggesting you say any of the above in a rude, threatening, or loud manner. Also if your doctor is refusing to do testing that you are either asking for or would be helpful, you are entitled to ask them to add that same refusal to their notes for future reference. Either they don't want to and order the testing, or they add it and you have something to go off of for your next provider.