Rain does not make in-city cycling significantly more dangerous, and is definitely fine for inexperienced cyclists. But if people cycle regularly, they aren't inexperienced, anyway.
In areas with frequent rain, people are practiced in carrying waterproof overclothes and such. Sub-zero temperatures, snow and ice can be a much bigger problem, of course, but good maintenance resolves a lot of that, too, as it does for cars.
As noted by drakonka, you continue to argue the infeasibility of something that works well for many cities/countries, citing things that those with experience know aren't a big problem. Sure, you can't just suddenly start cycling when your life/city is built around driving tens of miles, but a city/country can work towards biking in a way that has worked well around the world.