There are people doing very advanced and difficult things in classical mechanics, even if they aren't the problems or topics that show up in a freshman physics

There are people doing very advanced and difficult things in classical mechanics, even if they aren't the problems or topics that show up in a freshman physics course. There are also trivially easy quantum mechanics courses out there, so even if you are going to rank fields of physics by how "advanced" they are, I don't think going off the order they're taught to undergrads is reasonable.