It is a longstanding tradition discussed some here:
It is of course very fair and necessary to decide if something is likely to be something you’d appreciate/enjoy or not before you see it. I haven’t read the You Can See Everything thread yet precisely because my wife and I plan on seeing it this weekend and I have heard enough to know that it’s better to go in not knowing too much ahead of time. And we heard enough to know we want to see it. But posters shitting on movies sight unseen, usually sure that their opinion is more valid than those who have actually seen it, is not uncommon here.