Jonah, People who quote Juvenal’s elegant phrase as if it is a knock-down argument ignore Juvenal himself. Read in context, the meaning of the phrase is, essentially, “Well, it’s all very difficult, isn’t it?” The context is actually about as un-pc as you could ever get: how do you stop an immoral wife from behaving immorally? Certainly, the Satire as a whole comes to the conclusion “you might as well not bother,” but the phrase itself refers more to a greater problem of social breakdown than to the proposition in question. So in essence the answer is, as you say, the rest of us. Juvenal’s problem that there weren’t any of “us” left.