This is actually being rather generous. It's really a 2.5 but I had to pick a direction. The fight scenes are ok but uninspired and the writing is really really bad, especially in the dialogue. Everything is oversexualized and the way it's edited shows Joss Whedon tried to minimize that aspect as much as possible when he took over directing in the last month or so of film production. On the plus side it's colorful and the Flash has some funny lines with good delivery. Mostly a dud, but not a dumpster fire like Batman v Superman.

Full disclosure, we saw this movie last week but accidentally missed the first 30 minutes and didn't realize it until we got out and it wasn't as late as it should have been. We re-watched it today and my opinion of it actually didn't change that much. If it were a made for TV movie or a 90's direct to video special I would have said it wasn't too bad. But as it's a $300 million blockbuster it's hard to imagine how nobody on the production team threw up the red flag before it was released.