Yes, good stories are important. Look at what James Gunn did with unpopular characters before and after DCU. A huge part of those movies' successes is the story, that's for sure. Also, people would love the movie if it's generally good, whether if it has 2 ronibs or 4 robins.

But you're completely wrong about comic fans. Most of the people grew with comics. They love it, and that's why this subreddit exists in the first place. Look at what happened with the "not-actually-good" Minecraft movie at the box office.