What I used to call "grandious" or "pretentious" language when critiquing my kids' college papers. The voice of an FM radio announcer or a politician. For me it has the opposite effect intended: sounding insincere and possibly unreliable.
Maybe something like "write the following as if you were a CEO" or some other way of prompting it to switch to a terse, direct, "high" register, would improve the results.
It depends on the purpose of the writing though. If meant to convey with clarity, that was perhaps too much, but if meant to be enjoyed for its rhythm and imagery I say the more complexity the better.
What is grandious? Grandiose, or something similar?