I hate how it is common to advance a position to just state a conclusion as if it were a fact. You keep repeating the same thing over and over until it seems like a concensus has been reached instead of an actual argument reasoned from first principle.
This is no theft here. Any copyright would be flimsier than software patents. I love Studio Ghibli (including $500/seat festival tickets) but it's the heart and the detail that make them what they are. You cannot clone that. Just some surface similarity. If that's all you like about the movies... you really missed the point.
Imagine if in early cinema someone had tried to claim mustachioed villian, ditsy blonde, or dumb jock? These are just tropes and styles. Quality work goes much much much deeper, and that cannot be synthesised. I can AI generate a million engagement rings, but I cannot pick the perfect one that fits you and your partners love story.
PS- the best work they did was "When Marnie was There". Just fitted together perfectly.