simpleton vs someone

simpleton and someone both are nouns.

Word	Noun	Adjective	Verb	Adverb
simpleton	Yes	No	No	No
someone	Yes	No	No	No

As nouns, someone is a hypernym of simpleton; that is, someone is a word with a broader meaning than simpleton:

simpleton: a person lacking intelligence or common sense
someone: a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential

Other hypernyms of simpleton include individual, mortal, person, somebody, soul.

simpleton (noun)	someone (noun)
a person lacking intelligence or common sense	a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential