RT scores mean very little in the grand scheme of things for a film's success. Take the Transformers films for instance. They have gotten nothing but rotten scores, a couple of them in the teens, yet they still have a rabid audience that can't wait until the next one comes out. Bet you anything this next one clocks $1.3 billion without breaking a sweat.
DC needs to find the audience for their films and, sadly, the movie reviewers nor casual comic book movie fan hasn't warmed up to what they are offering. It seems to only appeal to hardcore DC and comic book fans, not the general public. If you want great RT scores, that's who you should aim for, the general public.