"Surely I could do a mediocre job as a CxO by parroting whatever is hot on Linkedin"

Having worked for a pretty decent CIO of a global business I'd say his main job was to travel about speak to other senior leaders and work out what business problems they had and try and work out, at a very high level, how technology would fit into that addressing those problems.

Just parroting latest technology trends would, I suspect, get you sacked within a few weeks.