Although the "communication skills" shortage you refer to is well understood amongst engineering types and a real problem on its own, I don't think this is solely to blame for the article's premise. For inventions that change behavior a lot, its not even enough to show a product, that still only allows the other person to see what they see, not what you see.
Email has been around for ages (the 60s in various early form), but it wasn't widely considered a killer app until the early to mid 90s.
On your first point, that's why things like the super-short "did you know that XYZ could do this...?" type of demos work great. Of course, see e.g. Kathy Sierra's writings for how to balance.
Re: your email example... You're missing the issue of network effects.
I'm not missing the issue of network effects. Or rather I'm not now as I can see clearly after the fact ;). But if you asked me in 1987 about email, I would have answered different. I think this is the whole point of the article. It is difficult to explain the future. Even the original inventors can't do it. Anyway, I think it was a nice article and worthy of some thought. Sometimes it is nice to know that maybe the right approach is just "do" and let the future do the explaining.
Email has been around for ages (the 60s in various early form), but it wasn't widely considered a killer app until the early to mid 90s.