I don't say this lightly - the fatal flaw is that they were written and directed by George Lucas.

Lucas is a fraud. The OT is great in spite of him. Marcia, Kurtz, Kasdan, Kazanjian, etc. are the real minds behind the OT's charm. George had the rough idea but those people made it happen. His ego has grown to the size of a planet over getting all the credit for SW.

Without any creative input or synergy, Lucas wrote a shitty first draft for each movie then filmed it. In the TPM documentary on the dvd you can see him looking at puppet models and telling the designers, "Oooh, I should write a character for this!"

The PT is inherently flawed because it had no reason to exist. In the end nothing happens. There's no tension. It's a shameless toy advertisement plugged with as many stupid looking aliens and weird robots as possible. There's no soul. There's no charm. Worse yet Lucas plagiarizes the OT incessantly because he is a shitty writer and has no original ideas. All the "poetry" and "rhyming" is him copying the work of better minds.