Metallica's MoP is the most overrated from the 80's material of the band, easily. Just think about 2 things:
-How much MoP thrashes for being considered one of the greatest albums of the style? barely the half of the songs have some thrash feeling, the rest are failed non thrashy experiments; The thing: Metallica trying Sabbath and failing, Sanitarium is the ballad to cash in the uprising glam movement (and they did it with Nothing else Matters, right?) Lepper is a boring and overlong shit with a decent midsection and nothing more, Orion is the hippie instrumental - thanx Cliff for your hippie contributions (cause Cliff was a huge fan of stuff like R.E.M and he brought all the acoustics and soft stuff to the band).
-Compared to the thrash albums released by the time, it feels simply inferior. How can Metallica match the intensity and raw brutality of Dark Angel's Darkness Descends? they can't. How Metallica can try to compete with the dark feeling of Slayer's Reign in Blood? no chance in hell!
I honestly think AFJA was some kind of resurrection for the band, but sadly they decided to listen to the producers, the media and decided to make the black album.