Fickle exs turned friends turned traitor

My ex had always said he wanted to keep being friends even after we broke up. We were doing that until a new girl showed up in his life. They're going out now and he has entirely transformed into a male imitation of his new girlfriend. With that I've been banished from hanging out with him and can only talk to him rarely if at all. She would of course prefer not at all. Zero contact. So much for how much he said he cared about me even as a friend. My father was right, at any moment a friend will toss you aside. Unfortunately ties are so weak these days that even some family will toss you aside if they have something to gain by it. It makes me sad to know this.