poor fish vs simple

poor fish and simple both are nouns.

Word	Noun	Adjective	Verb	Adverb
poor fish	Yes	No	No	No
simple	Yes	Yes	No	No

As nouns, simple is a hypernym of poor fish; that is, simple is a word with a broader meaning than poor fish:

Other hypernyms of poor fish include simpleton.

poor fish (noun)	simple (noun)
a person who is not very bright	a person lacking intelligence or common sense
	any herbaceous plant having medicinal properties

poor fish (adjective)	simple (adjective)
	(botany) of leaf shapes; of leaves having no divisions or subdivisions
	having few parts; not complex or complicated or involved
	easy and not involved or complicated
	exhibiting childlike simplicity and credulity
	unornamented
	lacking mental capacity and subtlety
	apart from anything else; without additions or modifications