The new ships will be a good addition to the Freestyle Fleet. I do believe that NCL knew, even during construction, that Epic's design had some major flaws. This was indicated when they tried to sell off, the partially completed, Epic after the second ship was canceled. It was not a purely economic decision.
I also believe that NCL did a lot of things right with Epic but they needed to get rid of the bad things, keep the good things and build two new ships that get it right.
I look forward to next week when I sail Epic. I can then formulate my own first hand opinions.