Type 2 Diabetes, non-congenital heart disease, and many forms of cancer are all metabolic in nature. We could have made a massive dent in this ourselves simply by eating properly and exercising. I know telling people that they are fat and it is going to kill them isn't politically correct these days, but sometimes you have to hurt feelings for the greater good.

As far as the rest of cancer goes, we simply didn't have the tech to do the things 10-40 years ago that we have now. The bitch of cancer is that it is unique to the individual. Things like CRISPR/CAS9 are already making massive breakthroughs and techniques based off this tech have already cured incurable cancer in a few test subjects (not to mention all the other things it can do......). Hell, not even 5 years ago could we think about editing DNA inline like a word processor can edit text. Now you can do it in your garage for a couple thousand dollars and a little know how.