dullness vs uninterestingness

dullness and uninterestingness both are nouns.

Word	Noun	Adjective	Verb	Adverb
dullness	Yes	No	No	No
uninterestingness	Yes	No	No	No

As nouns, uninterestingness is a hypernym of dullness; that is, uninterestingness is a word with a broader meaning than dullness:

dullness (noun)	uninterestingness (noun)
lack of sensibility	inability to capture or hold one's interest
without sharpness or clearness of edge or point
the quality of lacking interestingness
a lack of visual brightness
the quality of being slow to understand