This is from some Congressional testimony by economist Phil Levy:
In the absence of new agreements, there is a temptation to seek satisfaction through the aggressive use of venues such as the WTO dispute settlement mechanism -- litigation in lieu of negotiation. This poses a serious long-term threat to the viability of the WTO. It is not a legislative body and the United States government has generally objected when dispute settlement panels have taken an expansive view of their powers. The dispute settlement system is highly valuable as a means of settling factual disputes over the application [of] settled agreements. If the dispute settlement mechanism is used to resolve fundamentally political or unsettled points, it will eventually lose credibility and countries will cease to abide by its decisions.
I'm not sure how exactly to distinguish between "settling factual disputes over the application [of] settled agreements" and "fundamentally political or unsettled points," but I feel like we are towards the latter with aspects of the Cloves and Tuna-Dolphin cases, as well as the upcoming Seal Products case.
