There is something wrong with a movie that is less than 50%. Maybe you will like it, but there is a flaw in there somewhere that caused most people that review movies to not like it.
I agree with the last statement that there is something that caused most people that review movies to not like it.
But movie reviewers don't always accurately reflect the tastes of the public. There are lots of times I've seen significant mismatches on review aggregator sites between critics' reviews vs. reviews by average viewers. Granted, it's pretty rare to see a HUGE disparity (say, more than 30%), but it's quite common to see stuff where only 40% of reviewers liked it, but it has a 65% audience approval or whatever.
But, why on earth would I bother going to see it, when there are movies with 70, 80, 90% ratings to go see?
I guess I agree to the extent that I'm only going to actually pay to GO SEE a movie with really high potential. Given the expense and inconvenience, I'm going to a theater for a guaranteed winner these days. For the rest, I'll wait and watch at home (maybe).
That said, there are a number of prominent "critically acclaimed" films that I've really disliked. And I've had plenty of surprises where I've found films with less than 50% scores that have turned out to be a favorite. I may not take a chance in a theater on one, but I might for home viewing.
And certain genres often tend to produce low ratings. If you're into stereotypical action, horror, slasher, even dumb rom-coms, expect a lot of your genre to get less than 50% approval, because critics as a whole like something a little less full of standard tropes. But some people like those genres. (Note that I'm not one of them -- I'm not into ANY of those genres, but I realize that there's a HUGE market for many of them.)
Basically, to me again it comes down to the fact that critics are not necessarily representative of the public at large. If you understand the ways they are sometimes not representative, you can more accurately use their reviews. But just because 50% of critics don't like something doesn't mean there can't be a huge market for it... a fact that has been proven again and again.
And really, if you want to use reviews, you need to actually read reviews. Rotten Tomatoes and other aggregators just assign scores to reviews, but often what matters is NOT just whether the review is overly "positive" vs. "negative." Some things that are a turn-off for you might be a positive for me and vice-versa, and actually reading the review may help you understand why critics don't like it. A Rotten Tomatoes score is just a very crude and unnuanced metric.