Underrated and overrated are such subjective terms. If you don't think someone is the G.O.A.T. or the MVP that doesn't mean you are underrating them. And if you don't think a player should be waived, that doesn't mean you are overratting him. For example a player like Marcus Smart was overrated by many Celtics fans, while also being underrated by other Celtics fans. He was neither an All-Star, nor the cause of the team's losses.
Now Paul Pierce due to remaining in the public's eye since his retirement has done a ton of boasting of himself, which has drawn the ire of non-Celtics fans.