I think above all, most of Hayao Miyazaki's films have left some impact, at least to me. Most of the films gave me some joyful and inspirational feelings to create worlds using writing and drawing as my canvas. As long as those feelings are felt from watching
the other films that don't have the Hayao Miyazaki's touch then Studio Ghibli will do fine.
I saw his son's film and the animation wasn't the issue. It's just that the story he chose to go with wasn't that great. It had a lot of his father's charm but the content wasn't there. Which is something I think he can work on.
It is questionable right now if Goro Miyazaki will take over Studio Ghilbli. However,
Goro Miyazaki have stated that he is just at the
beginning of learning how to make animation films. I wonder if there are other candidates besides Goro Miyazaki who could provide that same charm.