I know you might jump down my throat since I’m a man saying this, but this feels overblown. There is no social standard that says headphones mean “leave me alone.” Most people wear headphones because they’re bored so they listen to some music. And plenty of people would welcome a conversation.
It is not rude to strike up a conversation with someone. Hell, this is expected of men. We are expected to make the first move. This is not demanding your time. This is not exerting power. You are free to reject the conversation in whatever way you see fit.
If they ignore your signal that you’re not interested in talking and they press on, then yes, I agree, that is rude.