The fact is that people still use desktop applications, and those applications by-and-large offer better integration and responsiveness than their online equivalents.
If anything, this is a direct assault on the entrenched desktop programming world. These platforms blur the line between thin and thick desktops, they enable a single standard for cross-platform development, and they open new frontiers for web-based developers. That is no small achievement!
Think of it another way: could you develop a desktop application for Windows, Mac, and Linux, with all the bells and whistles, as quickly as you can build a *single* online app? No? Well, now you can.