Why are movie critics so biased these days?

I agree, critics tend to think too much when it comes to movies. Why dont they turn their brains of for all of a couple of hours and just sit back and enjoyed themselves. In their minds if the movie has a big budget or has a few mainstream actors then they rate it poorly. It MUST be independant and arty and basically for the most part 'shyte' in my opinion. I aint dissing all independant or arty movies cos some are actually good but critics tend to side with them nonetheless