The stuff that is nice (easy train trips in and out of Tokyo, neighbourhood grocery stores, safety, etc..) are not relevant to tourists. The stuff that is touristy is also very samey. This is not very generous, but my view of local tourism boils down to a giant, beautifully-built temple - with Coca-Cola (TM) vending machines and cheap plastic junk for sale. Don't forget to go into a coffee shop and spend 800 yen just to have a place to sit (only to have no seats available).
With heavy crowding in places like Kyoto, and expensive lodging everywhere (rooms are priced per-person; not per room), it's hard to enjoy Japan as a domestic tourist. Having some historical context about Japan might make it better, but really, you can only see so much cracked concrete without getting bored.
Ski Trips, Onsens, and quality eats are great, but they just aren't worth the price of a plane ticket to Japan. As a domestic tourist, you can probably access the later two wherever you live.
The issue becomes worse for a potential international tourist in Japan. You have the language barrier, the length of trips (Korea is tolerable, but Singapore/HK/China/etc.. are long flights), and the ongoing loss of value of the Japanese yen. Between all this bad news, you also have an aging population who is not going to take the risk of catching Covid while abroad.
With all of the above, I can totally understand why someone would not find much value to traveling domestically or internationally from Japan.
In my case, the only value I derive is from visiting family or friends. I would probably never go again if I didn't have family there.