Well you can't argue with that. But what says you can't build a successful business around the web? Why can't you build a successful business with a desktop application?
I think the degree or pace of success will be different for a mobile, desktop or web app. I also think that an app that's on all three will be more likely to succeed than one that's only on one or two of these.
A couple or so years ago Microsoft had this vision of being on every screen or something. I'd never heard anything that made more sense as a vision statement from a tech giant. Then cloud came along, and they dropped that vision for the Azure/Office 365 push. That was a mistake.
[Edit] To be clear, Azure/Office 365 weren't mistakes - they were/are good. Dropping that vision statement was the mistake.