I like the wording of the question: “Can we credit the credit rating agencies?”
Unfortunately for now, they’re the best (read: closest to impartial) way that we have of assessing the risk of paper floated by various institutions. And, no, I don’t think that we can give them too much credit, because they are too “politically sensitive”.
For example, judging by what I read of the unfunded liabilities of various American states – and never mind the ongoing budget battles in more than half the states, who are often required by their own constitutions to balance their budgets year by year (and now find it difficult to do that) – I’m surprised that states’ credit ratings haven’t started to drop.
When that happens, and the debt becomes less than AAA or AAA+ rated, then a lot of financial institutions are not allowed to keep it on their books. So that could result in a fire sale of debt instruments, and another huge loss of wealth (because many retirees’ savings are in the form of bonds, and if the bonds become “worth less” – prior to being made “worthless”) then their retirements get a whole lot grimmer.