What is the subject of the following sentence?: The doubles match was more exciting.
"The" is a determiner adjective, "double" is a adjective here that needs not "s"
Keep in mind a single noun can be modified by many adjectives in a sentence.
Here match is a subject that is why sub-verb ==="was" indicates MACH. moreover both sub and object are noun/pronoun.
Again keep in mind, adjective needs not be always preceding of a nouns, it can be after the noun too!
Here, exciting is an adjective that modifies the Match. "More" is functioning here as an adverb modifying ===exciting.