Reality is that there is still a huge funding gap between the top teams and those further down. Japan have really supported their domestic and international teams, but not many other countries can do the same. Italy for example still only have two fully professional teams competing at close to a high level. For other countries many players have to go abroad to get high quality rugby. TBH there aren't many countries you can argue should have performed too much better. You could argue that France should have won a tournament by now given their resources. Ireland definitely should have reached a SF. Wales were unlucky not to reach a final, however generally the teams that reach the knock out stages are those who are better funded.