Dialogue is a subjective thing, and I don't think that's the major problem with AOTC. I believe that Lucas put a great deal of effort into the script, but frankly a lot of the structural issues and ways scenes are dealt with (as Bresson mentioned) smack of lazy writing. There's a visual effects term for a shot partway through the production pipeline: "could be better" or CBB. It's used for a shot that's adequate, but could still be tweaked to make it better. Time permitting, the artists will go keep working on it. The screenplay for AOTC, IMHO, is a solid CBB -- it works moderately well but could have been refined to really be a powerhouse story.