Aside from the poor defense, I think what really broke our back this game was the poor free throw shooting (again).
There was a point in 3rd quarter where we missed 4 free throws in a row (Randle, KCP) and that provided just enough seperation for the Mavs to close out the quarter up top.
For all Mejri's heroics in 4th quarter, the Mavs still allowed the Lakers to shoot 47.1% from the 3 and 54.8% overall. Therefore, the defense argument is a wash for this game. We needed to hit our free throws and box out the opponent properly. I think the team with Lonzo will be a good measure how we will fare in remaining of the season.