The problem of web app being in general less responsive than desktop app is just one of the many instances of unifying abstraction lowering things down.
We witnessed that with virtual machine, the industry invented multiple OS, and turn out we need to be able to run different apps on different OS at the same time and we invent (process) virtual machine to bridge the gap like Java Virtual Machine, or even VMWare or Hyper-V.
And then we have different databases, and then we have different data access abstraction layer out of it making it hard to use the best bit for each database vendors.
And then we invent phones, and have different types of phones, and then again we re-invent phonegap to unify the different phones, and paid the price for that.
Who knows what's next - the history is simply going to repeat itself, we create variations, and then we create performance losing unifying abstractions...
And such trend seems to be in this industry only, you never see someone build different building and then find a way to generalize building and make worse master building out of them.
Just knowing such a trend is rather useless, there is nothing we can do to stop that either. As long as there are multiple big vendors around that just won't stop.