Batman and Robin was exactly the movie they set out to make, live action cartoon, heavily inspired by Batman '66's camp. He wasn't aiming for "The Dark Knight".
To be fair that doesn't take away from the part of him thinking it was a good story. I love the classic Batman and the 1966 film is one of my favourites from that franchise but it's just a very naff script. Not sure if Goldsman would admit that but George Clooney has at least recently stated that he thought the script was terrible and that he believes Goldsman would say the same.