We used to live in a culture where expert opinions were respected, where scientists were listened to, where critics told us the best movies to go see.No, his opinion is as valid as anyone else's. It just concerns me the number of people who treat his opinions like Word of God. Not his fault, but Cult of Personality is always harmful.
Now, every voice is equal - regardless of how informed they are (or are not).
For me, when a critic has a very successful blog, is asked to write articles for major publications, and basically created the treatise on modern dungeon design, I listen to the guy about issues in gaming. I read his articles about how to improve other adventures (such as Rime of the Frost Maiden). When he goes through an adventure and rates it an F - and suggests there is essentially nothing worth saving - I listen to the guy.