The thing with the threes is that you can beat (and even dominate) your opponent in possessions, fouls and fg% but lose because you hit 4 or 5 threes and he hit 15 or 20. And well built teams have enough paint scoring to keep you from going +3 against them. That's (one of) the big weaknesses with the most common cookie: Moses ain't enough paint scoring by himself to keep you from loading up against the 3-point assault. If you go -3, you get owned and in foul trouble. If you keep it normal, you get into all kinds of foul trouble (which is atrocious as Moses is the only one that really gets to the line a lot, yet in this sim, nash, peja and allen all go a ton). And if you go +3, all of them have high enough efg% to still beat you, but in a 7-game series, it's usually enough.
That's why you see the cookie win 55+ games and then go down in the 2nd round or conference finals.