"I find McLuhan hard to understand partly because I’m just not that smart. Alan Kay on the other hand…" didn't understand him particularly well either, finding much of what he wrote "obscure and arguable". In that, he is hardly unusual:

http://marshallmcluhanspeaks.com/introduction

In fact, McLuhan put most of his emphasis on warning of the dangers of technology rather than being some design guru.

http://www.leaderu.com/orgs/probe/docs/mcluhan.html