Not that I like the prequels all that much, but this isn't 1950 and you don't need a single protagonist. A New Hop is also a massive cliche of the stereotypical hero story that has been done to death a million times over in the thousands of years literature has existed. It's why that movie was panned when it came out.
There's no single protagonist in the LOTR movies either, and those are all excellent.
I always thought the main hero in LOTR was Frodo.
It's not that it has to be traditional, but there has to be conflict with characaters; some overal thing that causes the character to change in some way.
This is supposed to be done for all characters really and no matter how small must be overcome by the end.
I put a little link here about types of conflict its pretty neat IMO. I am just sharing this link because it's interesting.
Conflict was my over all issue in the prequels.
Han for instance over comes a conflict; When you first meet him on Tatooine, he is all about the credits, not saving some princess (unless he gets a reward), but in the end he risked his life to save a person he hardly knew.
I felt that Anakin was too heroic from the get go and he never changed, same for all the characters. They just did not have the growth.
In fact overall the most heroic and developed character in Phantom iMenace, is probally, and i hate to say this...
Jar Jar, he was bansihed from his home and his people, went on a long quest and retuned with the Naboo to help defend his home.
IMO had Jar-Jar not been slap-stick comedy they could have done a lot with him. He could have still be comedic and young in the first film but 10 years later, he could have become a general and matured as a character. Instead he was unaffected by time completly, which is odd.