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.
although UEFA has made this tournament as competitive as possible, many countries consider the UEFA Nations League event not so serious, so it is only natural that many great countries have to fall from several dark horse teams, even though there are trophies up for grabs for the end of the season but many countries don't want to take this competition more seriously like the EURO or the World Cup, maybe we really hope that in the next 2-3 years the UEFA Nations League will become a more serious competition for European teams to participate in.