Polyamory would only work in literal paradise, so while technically true when saying "people should be polyamorus", it's like saying "people should fly" and then remaining silent as people jump off buildings instead of stepping in and clarifying that "people should fly" "under the correct conditions". What are "correct conditions"? In flying they are the materials a person needs in addendum to themselves to be able to fly. In polyamory a person needs conditions to make it possible as well. Most people cannot be polyamorus, because of the state of the world. Telling them to be, when they can't, and they don't know that, is the same as telling a child to go fly while they happen to be standing on a 10th story balcony. It's stupid at best, evil at worst.
@mushroomfemboy My ex was and probably still is. He tells everyone who will listen that they should be poly and had probably ruined lives. Also that guy Joe Rogain has on his podcast a lot, that guy who wrote Sex At Dawn is a literal toe sucking (I assume he sucks toes, he looks it) cuckold, who promotes cuckoldry and says, yes, everyone should be poly, as it's what's "natural".