It's about lack of imagination being envious of imagination. Those who are unable to suspend disbelief enough to enter into a story are eager to prevent others from doing so - it makes their cynicism look clever.

Of course , there are also plays/films/etc. which are simply so mediocre that all there is to do is carp at the poor effects... I once went ot see a production of Hamlet where the only redeeming feature was the set - a sort of maze-cum-climbing frame of staircases and balconies. I remember that set vividly.