It's much easier to score in basketball so that's not really relevant. Having played both, you're simply wrong. Spacing, defensive and offensive concepts, whether they are zone, man to man, or some combination of, are all very similar. Passing, ball movement, pick games, two man games, it's all almost identical. You think lacrosse is chaotic but that is because you don't know what you are looking at. It's far more complex for a reasons.
1) More players on bigger field.
2) Offsides
3) Room behind the goal
The last one makes it unique from most every sport other than hockey. It also forces defenses to guard an entire other area that isn't available in basketball. That alone makes it harder. Basketball is a very simple game. There is only so much 5 guys can do whether it's on offense or defense with no offsides.