I think also, that with the first trilogy, he had a lot of other people around him contributing and building with him, he had some genuine inspiration and interesting ideas, but that team being on equal footing with him allowed the that all to be executed properly.
There is a cultural issue where people tend to ascribe success of projects to lone individuals who lead projects, even while acknowledging the contributions of others, there is still this underlying assumption that a director is responsible for the sum of the parts. That the director is the one slotting the contributions together in a way that makes it work.
I think much of the same inspiration and ideas that he brought to the table in the first trilogy were still there in the later films, but the team around him was less empowered to contribute and shape the final product. How much of that was him having developed an ego, and how much of that was a result of the projects being conceptualized as belonging to him, and thus everyone else just working to fulfill his vision, rather than constructing a collective vision. And how much of that ego was foisted upon him due to how the culture at large conceptualizes the role of the director as singular author.
The second trilogy also leaned in to the kid stuff to a painful degree. I imagine because leaning in to kids was a good idea from a commercial standpoint, which helps pay for the massive unconstrained budget.