What's misplaced about Chalamet is he looks like a kid in front of Saoirse. Their pair is similar to Kate and Leo. where the female looks more mature... In terms of acting- I think you were a bit harsh on that Chalamet kid... this movie is not told linearly so the animated version of his which you think is missing is seen but in flashbacks in play enactments, dances in the hallways and on majority of his scenes are where he is love lorn, drunk and sad.