Sure they can but if everyone does it then they should expect to hear how it's overrated.
It's simple. Two people have opinions and both people get to speak them.
Overrated implies that many people are saying it's good. If twenty people say it's good and one person says "nope, not good. it's overrated" then it's not quite the same as two people having different opinions.
IMO "overrated" is a vague term that doesn't really mean anything other than to say "I don't like this thing that a lot of people like".