International hockey is an anomaly. Most of the countries that play it on top level are relatively small. Even Canada. Unless a country has passion, culture and traditions like Canada, Sweden or Finland, or human resources like USA or Russia, they are going to have up and down years.
Hockey also happens to be one of the sports where the gap between teams is reflected the most on the scorsheet due to skating and puckhandling being such complex skills. In football, find guys with good stamina and running speed and keep the score close. Same with basketball, just add height. But there are 0 chances in hockey against guys that outskate you.
Because U18 and U20 consist of players that are born within only few years, the gap can be even wider. Once a smaller country has its "down" year, it gets owned hard. Finland, Slovakia, Czechia, Switzerland, all had played in relegation rounds since 2010.
Reducing amount of teams to, say, 8, can be a solution. Will these 8 teams include Switzerland? Well, Switzerland lost 11-3 to USA just now. To 6 teams? Or 4? Well, its not really a tournament anymore. And will result in Switzerland that did not make the top division outplaying, say, Denmark, with the same 11-3 in the second division.
Sorry Canada, there is just no reason to make you play same three-four teams each year just for you to watch your NHL prospects. It will be boring for everyone else.