Lack of imagination.

Not imaginative.

unable to be imagined; inconceivable or mind-boggling; beyond belief

Done in a unimaginative manner; not creatively.

That has not been imagined.

To an extent or in a way that cannot be, or could not have been, imagined

(philosophy) The quality of being unimaginable.

present participle of unimagine

(transitive) To dismiss from the imagination; to make as though never imagined.

Third-person singular simple present indicative form of unimagine