Toward the end of the party, we have the unflattering description of husbands and wives and also the drunk who has crashed his car. what is fitzgerald's deeper message to us here?

I believe that his message is that everything we do has particular consequences. There people have had a lot of fun drinking and dancing while the party was still going, but after it ended, they were all way to drunk and disgusting, and obviously didn't think about how they would look or behave before they started drinking and having fun.