>Why "overrated" is a useless critique
Overrated means, just like the words says, that something is rated, or valued, higher than it deserves. Deserves, huh? This should throw up a flag right away, because how are you supposed to measure how much praise something deserves? To do this, you would have to objectively quantify how good an artist or a piece of art is, which is already impossible. You can argue that there are many qualities that could be quantified objectively, but it still falls apart because everyone values these qualities differently. Someone might agree with Schenkerian analysis that harmony is the most important thing in music, while someone else will definitely argue that innovation is.
You can't measure how 'good' a piece of art or an artist is, and as such it's impossible to measure how much praise it deserves, and how highly it deserves to be valued. Therefore it's idiotic to use a phrase such as "They are overrated". You are still free to say something like "I believe the critics overrated the historical importance of X", because not only are you specifying which aspect you think has been overrated, but you're also specifying who you think is overrating it, and that there's no objectivism at play here - you're simply stating that it is your subjective evaluation that differs from that of someone else's.
What you're actually saying when you use a term like "X are overrated" is really nothing other than "Others like X more than I do".