He didn't just own the property, he owned the company, the facilities, he put his own money into it, and would have been personally on the hook if the whole thing imploded (it did not, and was in fact wildly successful.)
If that doesn't earn a creator the right to do whatever the hell they please, I don't know what does.
Also; I'll take George's uncompromising artistic vision that may or may not be what the fans were expecting, over movies that are hollow, made-by-committee into blandness, and focus grouped to death, purely to service "fans" for maximum profitability any day.