Many players don't feel like playing these matches at all. Of course we see that they give interviews and that they say that they are looking forward to it and that they want to win, but that is simply a moral obligation to the fatherland. Kevin de Bruyne was recently one of the few players to come out publicly saying that he had no appetite for these conference leg matches at all. Now it can be a preparation for the World Cup, but that is a coincidence.
This competition was created with the aim of ending friendly games. Therefore, it is normal for many players to take these games less seriously. As the competition is still very recent, it still doesn't generate much motivation. But with three or four more years of competition, I believe that mentality will change a bit.