Messi is a player who usually gets support from other players like a legend they most rely on Messi, just like his situation in Argentina's national team and his previous team Barcelona, but still, after he joined PSG there were many other superstars players and Mbappe is one of them, Obviously, he won't receive the same respect and his unbalanced situation damaged him and effected on his performance.
lionel messi has realized this this season when a lot of scorn came to him which made him feel uncomfortable again in paris. In team depth as you said they don't really focus on supporting lionel messi to finish in every attack they do even mbappe being the main one in this category.
Lionel messi has so far scored 14 goals and recorded 14 assists so far, even this season can be said to be a more perfect season for him compared to his first time at psg. However, many fans do not pay respect to him even though he is a football legend who is able to anesthetize us from his skill with the ball on the field.