The Star Wars prequels are good for the same reason that Metropolis or Der Ring des Nibelungen are good. The characters are hammy and archetypical because the purpose is to immerse you in a vivid dreamscape of emotions and images. The point is not to be a "well-written" modern story.
It's supposed to be more like Greek drama or Kabuki theater.
Classic Gesamtkunstwerk of music, design, special effects, combat, romance, acrobatics, etc.