Why are the Mavs so bad at shooting?

[Branduil]

3pt shooting comes and goes. That's 
true for all teams. Can't totally depend on them. You have to have other ways to score.

Okay, so this is a take I see a lot, and while it's true that you need a diverse offense, modern NBA defenses are not stupid. You need shot creators, ball movement, off-ball movement, screens, cutters, etc., but if you don't have outside shooting none of that will matter. The modern NBA offense depends on being able to hit wide-open threes, that is true no matter what offense you run. You can't just say "well score inside if you can't hit threes!" because the other team will swarm the ball and force you to take those open threes. If you can't hit them, you'll lose.