Lens are like every other small teams that meet bigger clubs and have the desire to rise to the top but might not be able to so they settle for frustrating the bigger teams if not on a normal day, I think PSG would have them for dinner but since this is their coupe de France competition, virtually every teams participating would try to give it their best shot and Lens really gave it their all only they couldn't move to the next round because they were defeated on penalties by PSG.
Speaking about the results of the French Cup games, most Ligue 1 teams had difficulties to win, for example:
PSG,
Lille,
Brestois,
Le Havre,
Toulouse,
Nice,
Montpellier,
Lyon,
Auxerre,
Anger. It seems that all Ligue 1 teams are not taking this competition very seriously at this stage, perhaps if it were a final game they would take it very seriously. But the fact that they had so many difficulties shows that most Ligue 1 teams do not have a good quality B team.