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.
Friendly games won't be fully over of course, there will still be some right before the big tournaments (probably) but it certainly will drop them near zero levels if not zero. This idea of "ending friendlies" makes no sense to me, let the teams do whatever they want, why put another burden on the national teams when they are just there to represent their nations and not really make any money.
If it was up to the teams they could have just went with any game at any time against anyone they want and that would work for them, but since it's now all decided, they are facing teams that UEFA tells them and they play on the dates that UEFA tells them, which is limiting.