It's not really fair but WB AND Gunn have to earn back the fans and publics trust.
Gone are the days of having an automatic success because its called Superman.
First and foremost, it HAS to be a good film. Nothing else matters, not the title, not the actors, and not the 'plosions or action.
This is also not fair, but I doubt it even has a phenomenal opening weekend because of the DCEU's recent failures.
I'm pretty sure most of the public doesn't even realizes, or cares, that it's a brand new take and now called the DCU and not the DCEU, but if superman is good, it will have legs and stick around.