I think people are also worried because of what happened with JL last year. Good initial critic reviews, we were all like "PHEW! Ok, looks like this'll be in the 60's or 70's and be Fresh!" And then, there was one critic, I cant remember who, but he, after that initial wave of good positive reviews, popped everyone's bubble. He said something like, (im paraphrasing and exaggerating a bit) " enjoy the praise now guys, theres a ton of us critics who havent put our reactions out there because we dont wanna be harrassed. Well guess what, the calvary's coming!" And lo and behold the following week was an onslaught of "real" critics tearing the movie apart.
Obviously, the climate around Aquaman is not the same as JL's but just putting some perspective into the fear some have.