A pre-existing condition exclusion means that you're on your own for expenses arising from your pre-existing condition, or if you didn't report it when you applied for your health insurance, that you could have your health insurance retroactively cancelled, and have to pay back any money you received. It's really bad, but since some healthcare expenses seem to have more than tripled in the last 10 years, it's often worse today. I'd much rather pay 100% of $800 than 50% of $3000.
Medical care is expensive for a variety of reasons: nurse shortage, high-cost of training doctors, poor market conditions (opaque pricing that almost no layperson understands), cultural emphasis on fighting to the end rather than dying with dignity.
The cultural part probably won't change, we just have to accept that USA's culture (aka: "Full Code") is going to naturally result in more expensive health care. Its far more expensive to try to live than to accept death. Maybe someone out there will fight the cultural battle, but I don't see any political advantage in doing so.
Other issues can be worked on. Doctors aren't necessary for all care: nurses are sufficient for most cases. Lowering the cost of becoming a doctor likely would help too: if doctors had less medical bills, they might charge less for their services. (They HAVE to charge a lot to pay off those $200k+ to $300k+ student loans).
Medicine / Drugs is getting political... because changes to drug laws necessarily becomes a patent dispute. Should we allow drugs from India to become FDA-tested and imported? Or should we keep them banned for patent-law issues?
There's research issues: FDA is purely a placebo test. There's almost no comparative research going on at the federal level (Obamacare started up a comparative research group, but that group needs more funding and probably should also research on the PRICE of medical solutions. For whatever reason, research of prices is illegal). FDA is a very, very rigorous placebo test, but that's all it is. If a new drug comes out that's better than a placebo (but worse than standard treatment), it will pass the FDA. This means that doctors still have to research which drugs are most effective for their patients on their own.
Doctors can't trust insurance companies when they pay for research: insurance companies are looking for the cheapest solution. Drug companies are obviously biased, and may not conduct fair comparative trials. And unfortunately, those are the two major groups which sponsors research in the USA.