It depends on the audience. If it's highly rated, it's usually because of Eastern audiences. Western readers typically have different tastes and are uninterested in a certain pacing or story type. So calling something overrated is your own personal opinion, which is 100% fine! But acting like you're the forefront authority of manga ratings (how long you've been reading makes no difference, It doesn't make you an authority, it just tells us what your hobby is) and your decision on which is over or underrated is not. It's just you being arrogant and self-important, despite whatever you may think.
Keep your opinions to YOUR opinions. Nobody has the right to speak for anybody else.