It is unnatural to be engaged in a relationship with one person for an entire lifetime.
I would also like to add that polyamory can be (somewhat) compared to having multiple offsprings. People often ask me if I love one of my three partners more than the other two. I then ask them if they think their parents loved their siblings more, or if they have a preferred child of their own.
Only once you fully understand that is unreasonable and cruel to expect one single person to attend to ALL your needs for ALL your life can you allow yourself to have meaningful relationships with other people. They don't have to be romantic or sexual, but allowing yourself to experience emotional intimacy with multiple individuals can truly contribute to one's growth. You don't have to sleep with 3 people to be polyamorous, you need to fully and completely love them and be loved back.
"they don't have to be romantic or sexual"
Important to note.
Thanks for your valuable comment 🙏