I think that the main reason of Facebook's failure is that people need someone to listen to them. Facebook is just about sharing. People will hear you but you want someone to listen to you, eventually.

So,this feeling of being heard can only satisfy you temporarily until a certain point, meaning until you realize you need something more. Facebook has failed iked at what their main purpose is: communication.

Is there an alternative? Yeah, it's called life, listening, opportunities, etc.

My 2 cents.