A class action is an action where there are a large, possibly unknown, number of plaintiffs suing a single group of named defendants. With the thought process being that if a single case against a named defendant is won, then that same outcome would happen for every other plaintiff, and thus doing it once saves the court time.

What you're suggesting is more like a John Doe case where you sue a number of unknown entities, and that can be won, but at some point, the plaintiff has to name the John Does, so that they can defend themselves.