You seem to be assuming that the "audience" is one homogenous entity, and not different groups of people for each movie. It's far more likely that the people who gave Black Adam a high rating are people who are already DC enthusiasts who may well also dislike MCU movies, rather than this being one netural group of people who have all given their ratings to all the movies on the chart. It shows that some people like all the movies; it does not show that "audiences like both".

Or, the audience voting is highly partisan and people who love/hate either DC or Marvel turn out in great numbers to either inflate the scores of bad movies that they approve of, or to review-bomb arguably better movies that they disapprove of. In case of Captain Marvel, not so much because of their feelings towards the MCU.