Here's why:
* Adjectives describe nouns. They tell us more about the person, place, or thing the noun refers to.
* "Nothing" is a pronoun. It stands in place of a noun. In this case, it replaces the noun that would be the subject of the verb "looks".
The other words in the sentence are adjectives:
* "breezy" describes the day
* "lifeless" describes what nothing looks like