Jaylen may have the highest ceiling on this team and yeah that includes Kyrie. He's nowhere near the player he will become! Once his fadeaway is money, and it's getting there, and he develops a better handle he may remind people a lot of Kobe. His physical gifts may be greater then Kobe's now.
I really think the Celtics have been holding him back on purpose so he doesnt develop bad habits, get injured before the playoffs, etc. We all remember the player he was in last years post season and this year he will get more time off in the playoffs meaning he won't have to carry a team as much. In two more seasons Jaylen may very well be the best player on this, or another, team.