Wow...such passion...! Unfortunately, I do know some of the local critics here in Dallas, and while you may not care for their work, they do serve a purpose. I, like you, don't go to a movie based solely on a review, and yes, (as you state) they do add to the general conversation and marketplace of ideas; Roger Ebert is one such critic, as was Philip Wuntch here in Dallas.
What you find on the internet is written for the paper version before it finds its way online; even "Rotten Tomatoes" carries reviews from print sources and trade publications.
I have not heard the NPR pieces you link to, but if the capsule is accurate, I suspect the online "criticism" it refers to are very "celeb" and gossip driven (Ain't It Cool News being one such site, along with its many imitators.)
Unfortunately, legitimate online criticism not culled from the written page is the exception rather than the rule.