How can i trust these scores when everything is B or better....?
Theres some serious turds in that list.
Again, CinemaScores are always really, really high for franchise movies.
They take a poll of the opening night/weekend audience as they leave the movie and the scoring criteria are how much they liked it versus how much they expected to like it. The audience is made up almost entirely of hardcore DC fans, kids and their parents, and people who were already excited enough by the marketing to bother with the hassle of seeing a movie on opening weekend.
For a movie from a well known property to get a B+, that's a disaster. An A- is considered "okay", an A means you did your job, an A+ means you did great. A B is a colossal failure and anything below that is "fans hated this shit more than anything ever" tier. The people who are likely to be harsh on it are the ones who are likely to wait to see it.
This isn't people trying to review the movie and give it an objective score. This is how much the movie satisfied the most favorable sample of the audience possible. It tends to be a pretty decent predictor of how long of a theatrical run a movie will have; movies with high CinemaScores tend to have longer legs. CinemaScore has very little correlation with average review scores or awards or anything like that, though.
A high CinemaScore doesn't mean the movie is good, it just means they hit their target audience.
A low CinemaScore means either the movie drew in the wrong audience or it simply sucks. Movies that are brand new properties tend to have a wide variance in their CinemaScores. For example, Arrival was Denis Villeneuve's best-reviewed movie in terms of Rotten Tomatoes and Metacritic scores and it scored 8 Oscar nominations and turned a big profit, but it got the lowest CinemaScore of any of his films because the opening week audience went into it expecting a regular dumbass sci-fi alien flick. It's a great movie but the opening week audience didn't get what they wanted, which means the marketing failed.