It's simple really....and I can tell you get it. You just don't push the boundries with drum brakes. You don't put yourself in a position to have to make a long hard braking stop. Then they can fade. They were never made to stop on a dime and give you 5 cents change.
Well actually the only issues with drums on stock cars is that they were chronically undersized..... If they are sized right, and you use the right shoe material, they are 100% fine.
I raced with the stock rear drum setup on my Opel rally cars but they were huge for that size/weight of a rally car..... 9" diameter x 2" shoe... bigger than the early A cars rear drums, on a car several hundred pounds lighter! I would have the shoes lined with 'police service' linings, and upsize the rear wheel cylinders from 16 to 19 mm for more rear brake bias, and the rear drums would not fade even when the front discs and pads were getting hot and starting to fade a bit. So it is all in the sizing and lining, which Detroit did badly IMHO. OH, and JC Whitney shoes were notoriously bad LOL
The one situation that discs consistently do better is when soaking wet. Drums WILL have issues when water gets inside; water seems to get thrown out right away on a disc setup.