Really, you believe that? The two challenges that immediately come to mind are scaling and data mining, but there are a number of others. The use cases presented by the web have pushed distributed computing further than any other single thing in computing history. The web is just the interface the user interacts with... the stuff that's going on behind the scenes is still really interesting and very challenging. Building a web app requires both sides of the equation, it's not just writing some html.
Not really, most web apps are just CRUD (and MVC if you're lucky). What percentage of all web apps (remember, this includes apps that are only ever used on a corporate intranet) ever get to tackle scaling or data mining?
There are many examples of boring corporate non-webapp programs. Visual Basic was the most popular language once and it has nothing to do with web programming.
