It’s useful. The breakdown is usually followed by the party getting some therapy, owning its past mistakes, and finding a way forward. That happened after Goldwater with Nixon. It happened after McGovern with Carter. It even happened after Mondale, because Dukakis at least made a race of it.
This is not just an American phenomenon. It happens in all democracies. You can’t start back until you hit bottom, apologize sincerely for what you did wrong, get off the ragehol, then create an alternative worldview to the party in power from the ground up, one people find compelling.