I think he may be trying to get at the fact that we have 5 major browsers (IE, Chrome, Safari, Firefox, and Opera) and 5 platforms (Windows, Mac, Linux, iOS, and Android) that "web designers" build for.

Maybe, but we also have standards actually coming to the fore, such as HTML 5. I actually think it is getting a lot easier.

Compare that to one virtual machine (Flash) if you wanted, which although not "standardized", is controlled by a single company. iOS developers make this argument all the time as to why iOS is better to develop for.

There are tons of modern web technologies, often doing similar things, which are very complex.

I would say it's actually much less challenging than ever before since now they exist.