You spent 2 billion dollars developing a cure for x? I reverse engineered your cure for $30k (or just looked up your formula in your regulatory filings for free), so I can sell the same product for much cheaper than you since I don't have any development costs to recoup. If you can't protect your investment, you won't make the investment.

The problem here is not the patent system. The problem is relying on private for-profit industry to develop drugs. Not enough people get your ailment for a cure to be profitable? Sorry, you are SOL. Also, the current system incentivises developing maintenance drugs over cures. That's one of the big reasons Type 2 diabetes has met metformin, janumet, glipizide, farxiga, ozempic, etc. All of those drugs are symptom management rather than treatments. A treatment would be a financial disaster for big pharma.