If I put a bowl of M&Ms out on my front lawn, and then complain that nobody else refills it from time to time, is that the tragedy of the commons, or me just being a fool?
there's no point at which you putting M&Ms on your lawn can be self-sustaining. Both professional journalism and fish populations CAN be self-sustaining (from the perspective of individual consumers).
Also, even if your analogy did make sense, the end result would be no more M&Ms (aka no more professional journalism). That's the outcome we're trying to avoid.