I’m going to gently recommend that you don’t try to tell someone else about their own experiences. Poly isn’t only about sex and in fact has many attributes that are potentially healthier ways of being in relationships. Because there are no pre-set roles everything has to be talked about openly and honestly. It’s not perfect by any means and there are poly people who display human foibles, but another term for this way of living is ethical non-monogamy. It encourages participants to grow emotionally and to be better human beings. And if you don’t your partners have other options because not one person has to meet all your needs as with monogamy.
I have two male life partners that I am in loving and committed relationships with. I live with James and we have a child together. We also have a girlfriend together. I’m on a device where it’s hard to navigate easily but I recommend that you check out the Medium article Polyamory and the Struggle for Civil Rights. Here’s a quote, “In fact, there’s much monogamous couples can learn from their polyamorous peers: the increased emotional communication skills polyamory so often brings can also help disrupt destructive relationship patterns.”
I’ve also written extensively about my experiences with non-monogamy as a very positive, healthy, life and love affirming thing. What I’ve Learned About Love From Non-monogamy is probably the most popular but I’ve also written What the Vanilla World Can Learn About Consent From a Sex Club. We didn’t start out in this lifestyle but after deciding together to embrace it, we’ve grown as individuals and as a couple. I have healed a lot of the wounding that mainstream society inflicted upon me around my sexuality and comfort in my own body. It’s true that it’s perhaps not for everyone but a lot of that has to do with the level of actually dealing with yourself, your baggage and insecurities that ethical non-monogamy requires. E. L. Byrne also writes extensively about her poly life and how much joy and healing it has brought to her. I highly recommend that you learn more about this topic from those who are living it. The experience you described is but one story amongst many.