Yes? Tons of successful polyamorous close friends? I would basically say that every relationship I know of that started with both parties happy to be polyamoro

Yes? Tons of successful polyamorous close friends? I would basically say that every relationship I know of that started with both parties happy to be polyamorous had a happy story arc, whether it ended eventually or not (N=~8). Sometimes a non-primary partner would be unsatisfied and move on, and occasionally primary relationships evolve to something less than primary, but that’s “working as intended”, by my book. Now, I will agree that trying to fix a broken monogamous relationship by opening it up is a recipe for disaster. Perhaps all the polyamorous relationships you’ve observed started out monogamous? It’s also true that polyamory is gargantuan amount of work, it’s in many ways a bigger commitment than monogamy. You have way more dyads needing active and thoughtful communication, and so people whose motivation for polyamory is not wanting commitment are terrible at polyamory. But once you get past those two hurdles (doing polyamory under duress, thinking polyamory is less work, when it’s more), it works great for people who are into it.