Here's why:
* Pronouns stand in for nouns. Examples include: I, you, he, she, it, we, they, me, him, her, us, them, mine, yours, his, hers, ours, theirs.
* Nominative pronouns are the pronouns that function as the subject of a verb. Examples include: I, you, he, she, it, we, they.
"All" is a determiner. Determiners are words that come before nouns and modify them. They tell us how much, how many, or which noun we are referring to.
Examples of how "all" functions as a determiner:
* All the students were excited for the field trip.
* I ate all the cookies.
Let me know if you'd like to explore other types of words or grammatical concepts!