I believe it is up to Jaylen to accept his role and become a much more effective basketball player. Seems Ime has cured much of Smart's bad habits and has also improved Tatum's decision making, ball movement and turnover problems, but Jaylen continues to make the same dumb plays over and over and to get lost when playing the help side on defense.
The guy just keeps forcing his shaky dribble into traffic and getting stripped or losing his balance and throwing a bad pass. I dread those top-of-the-key isos he loves to go into with his "bag of tricks" dribble. Even if he doesn't turn the ball over, those drives often kill the offense and stop ball movement. Brown did pull up a few times last nite and took the open 15-foot jumper instead of forcing himself into the teeth of the defense.
If I were Brown, my focus would be, "What strengths do I need to use more of to help this team win. How can I be an offensive support to Tatum and not an impediment (sometimes). What bad habits do I need to reduce to be a better player to help us win titles ?" Put his ego aside and do what is best for the team. Maybe a cliche' but Brown could make this team that much better if he would play to his strengths and let the game come to him instead of sometimes continuing to force his offense. Also, he could be a great defender with his body, his length and athleticism, but that has not quite happened. Good defender, but could be so much better.
Jaylen Brown appears to me to be a team-first guy, but he has to figure out, with help from the coaching staff,
how to play much smarter basketball and help this team instead of disrupting it.