Arguing you should not write "complex" things or "formal" things becuase of poor attention spans just makes me sad about the state of literacy.
I mean it's advice from the same man who thought "delve" - a 6000 year old, monosyllabic word used by Shakespeare and Tolkien - was too complicated and should not be used.
I am not sure we should be taking him as a literary authority.
Unnecessary complex and formal writimg is just a poor writing. It is harder to write clearly and simply.