Nicotine isn't bad. There are plenty of ways people use nicotine in just as benign a way as many people use caffeine.

You've missed the far-and-above most beneficial effect of switching to vaping, which is getting rid of inhaling the huge category of carcinogens that come with inhaling partially burned solid fuel.

Cigarettes don't give you cancer because of nicotine. They give you cancer because of partially burned solid fuel.