"Motherfucker" is an actual pronoun

No, it's a noun, as are "asshole", "son of a bitch" (noun phrase), "fucker," "cunt," and "bastard." Pronouns are not "subcategories of nouns" either, which is the latest sleight of hand by academic linguists to legitimize the idiotic gender craze by validating the nonsense crazy people say about themselves. Pronouns REPLACE nouns, usually to avoid clumsy wordiness and awkward repetition of nouns.

Here's an informative page about pronouns: https://www.englishclub.com/grammar/pronouns.htm