Scott Payne begs me to acknowledge that "the criticism progressives keep hurling at the President and many of their fellow Democrats is a feature of American politics, not a bug." Bernstein says much of what needs to be said in response:
If one believes that the only reason a policy is not enacted must be that the president did not favor it, then one is going to make a lot of poor choices in deciding how to advocate for policies. Indeed, the hallmark of the American system of government is that it's easy to stop policy change. That certainly does not mean that one should never criticize the president! Sometimes, that's going to be the best way to place pressure. All it means is that criticisms (or support) of the president should be based on knowledge, and good judgment.