The thing about 3X3 is that you play a variety of different teams that require different matchups. In Colliers case it is not just about how she plays against one team but the other types of teams that they faced. A Big and every other team member, is also supposed to provide help defense because in 3X3 it is easier for players to take their man to the hoop. Watching the games Collier was deficient in that respect. The Netherlands was an ideal matchup for her, while the other games were not. I am not saying that she is not a good 5X5 player, rather that for the 3X3 game they should have gotten either a taller/bigger player or a quicker one. She was a tweener in that respect. Alarie was a much better fit. She often carried the team in some of the earlier games.
For example in the Last 3X3 the USA competed in their big was Bailey, who while also not as quick, totally dominated inside when she got the ball. Something that Collier could not do. The weak link on that team was Littleton who could not hit her shots, but more importantly, was slow as molasses. Williams was the third best player on that team. DeCosta dominated those games because she had the right combination of skills. She was a quick athletic player who excelled in space but also could defend in the post when necessary. Alarie was the closest they had to fit that criterion.
Some of the players that other countries have on their team's skills do not translate as well on a 5X5 game but are well suited to 3X3. In this game athleticism and outside shooting are most important. Players are always going to have off shooting games, but when that happens they have to contribute on defense.