The World Championships is I think the better tournament since it involves professional players. The World Juniors is the better proximation of overall hockey strength since it's a "best-on-best" of Junior players (some people argue this point because of 19 year old NHL players that don't play in it, but to me, those are no longer "Junior" players and in the long-run it all evens out a bit... Canada may miss more guys than Germany but that one German guy not playing likely has a bigger impact than a single Canadian because they have more depth)... other than for smaller countries that don't have a lot of NHL players (i.e., you can make a better guess as to where Norway and Austria stack up with each other via the World Championships).
The World Championships biggest issue for North Americans is that they run concurrently with the NHL Playoffs. That alone just makes them a bit of a non-starter for popularity purposes. American NHL fans are going to watch their NHL teams in the Playoffs, they don't really care about a hodge-podge team of American-born players playing in some tournament. And the other big factor that runs with that is that the tournament is often in Europe (which makes sense, the sheer raw number (not weighted) of International Teams skews European so if everyone got a turn hosting, it'd be in Europe much more often), so that means the games are on at inconvenient times.
Even amongst NHL fans, the World Juniors aren't super popular amongst general fans, but the USNDTP has succeeded in building excitement/enthusiasm amongst the players, whereas back in the 1990s it was more so a random collection of players that didn't much reason to care to be there. For fans, the tournament being so frequently held in Canada makes it easy to watch, but the fact that the tournament is so often in Canada, or at best, a border town that is easy for Canadian fans to access, does show that it doesn't have nearly the same degree of enthusiasm as it does up north. The games are aired on NHL Network and they don't get a lot of attention quite frankly. It's a small contingent of diehard Team USA fans but it doesn't go too much further. I don't think it's super reasonable to expect NHL players to have a buy-in for the world championships to the same level. There are just too many factors going against it.
Even amongst a more popular sport like Basketball, there isn't much enthusiasm for the World Championships (now re-named the World Cup). We are a bit spoiled to have so many of the world's top sporting leagues in our country that.. for as patriotic as people claim Americans to be... international sporting competition isn't ultimately that big of a deal compared to our domestic leagues which people already regard as the "best of the best" going at it, with lots of local community pride/spirit behind it. Once a player hits the NHL, that becomes their job/primary focus. Risking injury and just overall wear and tear to go play in a competition that isn't seen as having much value in and of itself just doesn't make sense.
I think it is worth pointing out though, that the 'raw depth' approach has been producing better results. The USA has just been stuck on that Semifinal barrier. Last year, they lost 4-3 to the eventual Gold Medal winners and host nation, Finland in the semifinals, albeit after a pretty poor group stage. It was a pretty competitive game, with shots 28-26 in favor of the U.S. The year before they took first place in the group stage in a group that featured Canada and Finland, and ultimately fell to Canada 4-2 in the Semifinals and then won the Bronze Medal game. The 2020 tournament was cancelled. 2019 was a bad showing. 2018 was another bronze medal finish. 2017 finished first in the group stage in a group with Russia and Sweden, but drew a tough matchup with Finland in the Quarters and got knocked out. 2016 was another semifinal appearance. 2015 another group stage win and bronze medal finish.
Those are much better results than what the USA used to see. Canada will likely always have the edge on the "raw depth" approach of winning even with high NHL Playoff/decline invitations rate (and frankly, knowing they can win and the more intertwined nature of Hockey in Canadian identity means they will get better participation), so it's tricky to beat them, let alone the Europeans that have their Euro-Pros available and more enthusiasm from eliminated NHL stars. However, I do expect with NHL numbers by nationality being what they are (highest American rates ever) and given the results the last 8 years or so, an American team will break through one of these days. It took until 2004 for the USA to win their first world juniors gold, and 2010 for them to win their second, but since then the USA has been competitive at that level. I expect the same thing to happen at the World Championships as enough time goes by. Hopefully once the first team wins a Gold Medal, other players will see that it is possible and they'll want to join the party next time.