One important thing I think that distinguishes the two is that in 4-6, things took time to develop: stories, relationships, dialogue. Things feel so rushed in 1-3. I know GL was trying to fit in many plot elements, action sequences and such. But ultimately the overall was sacrificed. Think about the important dialogue scenes in 4-6; then compare them to the important ones in 1-3. Anakin declaring his love for Padme by the fire, for example. That scene lasts, what, 20 seconds? And it follows some equally abrupt and weak scenes of them together. “Obi-Wan doesn’t like when I use the force to move fruit across the table blah blah blah.” Their relationship doesn’t have time to develop, so that we don’t accept that there could be one. But yet, when Leia tells Han she loves him, we don’t doubt her for a second, because of how it was build up.
This makes more sense in my mind than it does now that I read this…