"[...] surely we can build a simple app that everybody can use that does even one useful thing, like, say, mitigate the Erroneous Priorities Effect when you're attending a meeting."

This, I believe is a good old engineering problem. The hard (maybe not wicked) problem is getting people to use it. Ah yes, and if you really want to help solve the wicked problems, it can't just be any people but rather those who make/influence important decisions.