I think you're reading into the accuracy of Japanese politeness too much, and also its overall meaning.
People are polite here. For the most part, they avoid any sort of public conflict. But there are Japanese who know this is the case, and ride the system because of it. They are utterly rude, since no one else will step up to tell them off.
At the same time, the politeness is a form of distance. Like in the West, more and more Japanese never acknowledge the people living around them. I've never talked to my neighbors in a decade here, and when I run into them, they put their heads down, more often than not. I have a child, so occasionally, while carrying a baby, I've had polite chat with another parent in an elevator.
But politeness and respect is very different from love and closeness. As a relatively healthy person with a family, I'm happy with the situation, but if I were lonely/single/ on the second half of life, I could see why it could be isolating, and exacerbate the problem.
The issue of suicide is also a little peculiar to Japan, where traditionally it was an honorable thing, whereas in the West, it was a sin. That makes the perception of it different. Not to say it's okay, but I think it's considered sad and regrettable in Japan, compared to the West, where I'd say it's considered a cruelty to those left living. Japan Rail tried to institutionalise this idea by charging families of people who killed themselves with their trains. I don't know that it worked.