While I agree that we could say that we are not linear in our thinking, I believe going from that to saying Powepoint is one of the worst contributions is a bit far-fetched in my humble opinion.
Having said that, a lot of times there is a need for linear presentations. While our minds may be shooting ideas in all directions in a clearly NOT linear way, our speech is linear and so we must organize the ideas in such way to communicate them.
Otherwise we would simply spit random concepts and thoughts as they come into our heads and while that might make a lot of sense to us, it would be impossible for our audience to understand it.
I also believe that categorizing one way or another of thinking in terms of inspiring, boring, rigid, fluid has nothing to do with whether the process is linear or not. You could have a boring and uninspired brainstorming session and at the same time have a fluid linear presentation or the other way around, so this association to each thinking model is in my opinion not true.
Still, this article certainly gave me a kick to rethink a few ideas of my own, so I thank you for that.