I had an 800 for 10 years. That thing was ancient, but the touch screen worked fine. Rain, gloves, whatever. It's not a smartphone. Probably the extremely low resolution of all Garmins helps with that, good phones have more pixels per inch than the 830 has total. The things you're touching aren't as small. Drops of water or sweat on the screen don't make it go crazy the way they do with a phone either.
My Garmin watch has routable maps, but no touch screen. Interacting with maps with buttons works, but holy crap it's tedious to zoom in and out and scroll and really get value out of them. The point of buying a bike computer is being able to use it on the bike instead of having to stop and get out your phone. So it makes sense that it should be easy to use quickly with as little of your attention as possible. And touch screens are for sure the way to go for that with mapping.