WordNet sense 1 (not fanciful or imaginative):

matter-of-fact

WordNet sense 2 (not rhetorical):

unrhetorical

WordNet sense 3 (lacking wit or imagination):

earthbound, pedestrian, prosy

WordNet sense 4 (arousing no interest or attention or curiosity or excitement):

uninteresting

WordNet sense 5 (not challenging; dull and lacking excitement):

commonplace, humdrum, unglamorous, unglamourous