I don't think there are any flaws. I just remember seeing it in the theater when it was first released and thinking this is the greatest movie ever made! Then I watch it years, no, decades later with my kids and saying to myself, did I really think this was the greatest film ever made?
I think my worldview has changed since the sixties.
It's a good movie, just not world class, best movie caliber.
Just my opinion.
Well its regarded as world class, the world over. :)