PE skills are on the decline because they simply aren't that useful anymore.
20 years ago, you needed to tell the presence and severity of mitral stenosis based on physical exam.
Now, all you need to hear is a murmur and the echo will do the rest.
Physicians are smart people. They allow skills to erode which aren't very important anymore.
I'm willing to bet the physical exam skills of most cardiologists isn't much better than medicine attendings. And will continue to get worse as the years go on.