unremarkable vs routine

unremarkable is not a noun while routine is a noun.

Word	Noun	Adjective	Verb	Adverb
unremarkable	No	Yes	No	No
routine	Yes	Yes	No	No

As adjectives, unremarkable and routine are synonyms defined as:

Other synonyms of unremarkable include everyday, mundane, quotidian, workaday.

unremarkable (noun)	routine (noun)
	an unvarying or habitual method or procedure
	a set sequence of steps, part of larger computer program
	a short performance that is part of a longer program

unremarkable (adjective)	routine (adjective)
found in the ordinary course of events	found in the ordinary course of events