Has everyone gone insane? The web is absolutely incredible and JavaScript is absolutely killing it as a portable application language. Remember the dark days of flash? Stop complaining.
It takes a while to load (not really, 100ms + download), but after that it is silky smooth due to client side rendering (faster than downloading more html) and caching.
On the most demanding page, heap usage is a little more than 20mb.
Sure, there are a lot of websites which are slow and huge memory hogs. But that goes for many native apps as well.
Meanwhile, how fast Google Docs loads depends entirely on the speed of my internet connection at the time. Good luck even opening it at all if your connection is crappy, flaky, if any of the ISPs between you and Google have congestion issues, or if there's a transient latency problem in one of the dozens of server pools that makes up an app like Docs.