i LOVE music criticism, film criticism etc. when it's good it can offer new perspectives, explain why something has the effect that it does, explain where something fits into historical context, analyse the themes at play in the music, etcetc. i get a kick out of reading that stuff, it's not that it helps me form opinions so much as it explains/illuminates my reactions and often enrichens those reactions by opening my mind to other aspects/interpretations of the work i hadn't fully considered. i have no issue with people who just wanna throw something on that sounds cool and not think about it, but i love approaching the arts in an analytical way, discovering fresh perspectives, developing my tastes etc. and i do my best to understand the appeal of stuff that's not immediately accessible - if i hadn't done that in the first place, i doubt i'd ever have developed a love for extreme metal.
the problem is the vast majority of metal reviewers write like they're 15 years old (probably because they are), and seem more interested in sounding knowledgable and preaching to the choir than actually bringing something new to the conversation.