While I'm not suggesting that UML is necessarily the solution, I hope it's not, but the observation that so few developers touch anything that just looks like UML is a good indication that a lot of software is in fact NOT designed, it's just sort of hobbled together from a few sketches on a whiteboard.

I hope that people say they hate UML and then just make UML (class, database, activity, ..) diagrams according to their own conventions, but I am afraid you are right and that a lot of software is just "hobbled together"...