Yes the Japanese society is very closed. With the following consequences:

1- They are very stubborn, they think they are right and historically this has given them the right to conquer and humiliate everybody around them. This is why the US had to send them TWO atomic bombs (one was not enough to change the mentality).

2- Japan has been in fiscal/financial stagnation since the 1990s, can't increase its inflation (required for growth), no matter what it tries. No growth in sight for its economy.

3- Their workforce is getting old and there is almost nobody to replace it. They don't know who will take care of the old workers when they hit their late 60s, 70s and 80s. Their society is so closed that it is shrinking itself into oblivion. The load will be on the shoulders of the tiny generation of millennials (imagine the taxes they will have to pay).

4- They have no cultural impact on the rest of the world. Nobody wants to be like them. If their islands sank into the ocean overnight, the world would not cry.