I would agree that with a score under 500 and two cards close to max, a risk analysis is not likely to result in grant of new credit at a level capable of paying off a substantial portion of the existing debt. It may even cause a drop in score by adding an inquiry.
Even if you were to obtain a new card, would you have the discipline to use it ONLY to pay other, existing debt, or would you be tempted to use it to actually increase your existing debt, and thus possibly the risk of becoming delinquent?
High current % util on all cards usually demonstrates overuse of discretionary revolving credit, with substantially increased risk of default.