I would love to have made two changes.
One, I would like to have seen girl comics continue to be a priority after the fifties. When comics started, they made them for EVERYONE, but that dwindled away after the war, for a number of reasons having little to do with economics. That cost us dearly over the decades.
And I wish the major companies had not put ALL their eggs in the direct market. I love comics shops to pieces, but this strategy almost eliminated the idea of comics for all ages for a number of years. I’m over-simplifying, but it had a huge impact.