As a web developer I believe the problem and the bottleneck has and always will be the browsers. If there was an easy way to give our users what they want (flashy, ajaxy webapps) without breaking the web I'm sure developers would be all for it. But for now it is viewed as a time intensive, value add to do these properly. Web developers will always be a step ahead of the browsers and therefore have to resort to breaking the web in order to achieve the functionality their users/managers pay them to create.
The only way this problem will be resolved is for more of your "true" computer scientists to start working on browsers. However, at the moment, many of them are making too much money at their consulting firms fixing the websites created by graphic designers.
Users don't want hashbangs. They want faster loading content. Hashbangs are a kludge to get it. This is just one example of the issues that we're running up against with trying to extend HTTP, HTML, and browser technology into an application platform. It's just not suited.
HTML 5 is the right answer to the wrong problem. The problem is not how to make HTML more expressive and more powerful. The problem is how to serve applications to users. We need an open standard for WebStart/ClickOnce, not a hack on top of a hack on top of HTML to make web pages appear like applications (with every web designer's own notions as to how to render UI elements and display notifications and control flow, etc.).
Next time you see a JQuery modal dialog, ask yourself, "why did someone on the client level have to write this code? Why wasn't it part of the platform?" Why do we have competing implementations of modal dialogs on web apps, in today's day and age? And it's often represented by a severely nested DIV in a section of code that has no meaning to the modal itself. Semantic markup, for sure.
The only way this problem will be resolved is for more of your "true" computer scientists to start working on browsers. However, at the moment, many of them are making too much money at their consulting firms fixing the websites created by graphic designers.