I think you are way ahead of the game to be able to recognize how unrealistic their approach was and to decline to continue. You are likely right, they don't know what they are doing and it very likely would end in disaster. Hopefully they will educate themselves.
We are new to poly ourselves and are trying to learn as much as we can by reading forums and stories and meeting people who successfully live a love-full life.
At least you will know what to watch out for in future dating. Half the battle seems to be in clearly knowing/understanding what you want...the other half is connecting with others who do to and having it all mesh in a healthy way.
Best of luck to you.