There a few reasons why international competitions aren't as high standard as club competitions.
Let's compare the World Cup to the national leagues and the Champions League/Europa League. The World Cup doesn't have home and away games, it's 3 (or 2 starting in 2026) and your tournament could be up. Also it only happens once every four years unlike the national leagues which happen every year. These are probably why teams are much more cautious. Then there is also the fact that club teams play together all year while national team players are kind of thrown together.