I've had a few times around here where it's raining lightly, and then the sky just drops out and I'm in a downpour. Of course, the wipers don't react quickly, which isn't surprising. They didn't react that quickly in my previous car (2013 Ford Taurus) either, but the difference is that my previous car had a stalk control where I could quickly adjust it while keeping my eyes on the road.
I think I heard something about them putting it on the touch screen? Honestly, I don't understand Tesla's obsession with putting everything as a digital control. I know they want to ensure that controls lack static positions, as that makes digital + physical control much more difficult. For example, with a standard wiper stalk control, if you adjusted it on the touch screen, the wheel would need to move to the proper spot. That's why I'd be fine with something like the existing steering wheel scroll wheels... just a big bigger. They should have very defined stops, but all they do is scroll through the settings in the same order as the screen (OFF > 1 > 2 > 3 > AUTO). So, if I'm on AUTO and I need some heavy windshield wiping, I just scroll down one stop.