Japan is actually relatively short on things to do considering how many tourists they get. There's some proposals to build another large theme park in Yokohama IIRC.
Source: I did just that this past New Year.
Weird, I felt the opposite vibe. When I spent 3 weeks during spring over there, as a tourist, it seemed like there was endless stuff to do, see and enjoy. "Touristy" Japan feels like a theme park in itself. And for "proper" theme things, we only did Ghibli Museum.
https://www.bloomberg.com/opinion/articles/2023-09-05/tokyo-...
What did your itinerary look like?