For an interesting instance on how onetime Obama enthusiasts have soured on the 44th president, you could do worse than read James Traub's piece in foreignpolicy.com. Traub comes close to saying that, well, Americans' abilities to shape the world are limited and no president could have done much better than Obama has -- but he also seems to think it is both possible and desirable for American leadership to do better.
At one point he summarizes one of the things he liked about Obama in 2008: “Obama vowed to make American power more acceptable by deploying a language and a statecraft of mutuality and respect rather than highhandedness and unilateralism. He would seek international consensus on neglected global issues such as climate change and nuclear proliferation.”
My own view is that the chance that “a statecraft of mutuality and respect” toward enemy or adversary actors was not going to be very successful in making the world safer for Americans and American values, and that its main appeal to people like Traub was that it made them feel more virtuous and comfortable. Clearly he doesn’t feel so comfortable now, and I suspect he’s not the only one.