Or probably Jason Kidd is part of the problem? it seems that he can't bring the team into chemistry, just like in this game, they have a good chance to win although I have the underdog Atlanta to beat them.
And that has been the story of the Dallas, the bench is not helping, or at least if they, it's always feel short of expectations.
There is always some missing pieces and it's hard to pinpoint whether it was the coaching of the players themselves.
Dallas IMO is a better team with him. In terms of a roster, I think they already have a good one but most are young and do not have a good experience in the playoffs. Luka is also young, maybe Luka will only win a championship if he will follow the style of Lebron to create a super team. Right now, Dallas is not a superteam, they have the best player Luka but he is not surrounded with a consistent players.
A good example of a team that has good role players are the Nuggets, their best player is Jokic but he can rely on his teammates to help him win.