[Dismas]

If you're young, just stay single and enjoy yourself, 9.9/10 poly will have you fucked up, it's unnatural.

I feel like it's unnatural, and an excuse to live out a fantasy. That's my opinion though. Your life, your decision.

This is the narrative I'm trying to challenge though, why is a committed polycule implicitly any more "unnatural" or unstable compared to a Western, Catholic and State influenced, life partner monogamous relationship?

Monogamy is normalized because it's simpler. Legislation and taxes also play a role.

When you're dealing with multiple people, a lot goes into ensuring the emotional needs of everyone involved are met. Guys normally have a problem keeping just one woman happy, so I really wouldn't recommend polyamory to the average person. The more people you add to the equation, the more dynamic things become.

The polyamorous friends I had were very sexual people. Selfishness/jealousy were recurring themes and they only remained polyamorous about 2-3 years. Not saying that will be the case for you, but you should consider whether the relationships you're forming will be long-term or entirely sexual.