Yeah, modern ones have a decocker to fix that problem. I’ve never looked up how they work exactly. I do know that some revolvers also have a little piece that comes up to block the hammer from striking.
The historic design is certainly unsafe, but in those days, guns were rare and expensive enough that if you had one, you were already going to be trained on it. (Also, compared to a semi-auto pistol slide spring, revolver hammer springs are surprisingly weak. The only time I’ve had to do it, in a safety class, I was using so much force to hold the hammer up, I didn’t realize I had to let off to let it down.)