The view that web apps can only be for simple things is a dated perspective, but also probably a symptom of the fact that it's not really possible to take full advantage of many CPU cores in a web application.

An in-browser photo editor or 3D modeling software would be expected to run much better and apply complex effects or render models much faster on high-end hardware. It sort of works this way with WebGL content, but even there you're limited to feeding the render pipeline with a single thread.

I want the web as a platform to succeed. It is the only truly universal runtime and with some care it could offer very few performance trade-offs. I sincerely hope tools like servo and others unlock this potential.