Anyone notice that ten first round picks were ranked below 100 out of high school? As were another 11 second round picks. That is not including foreign players (other than Hachimura, who was ranked 148). Six draftees, including three first rounders, were totally unranked. So don’t despair when you see SU guys not in the top 100. Doesn’t really mean much.
Every year there are 30 5-star players, which have a very high chance of being drafted, say 70%. That means there would be 0.7 x 30 = 20 5-star players drafted.
There are 300+ 3-star players, who have a small chance of being drafted, say 10%. That means there would be 0.1 x 300 = 30 3-star players drafted.
You're looking at the end result, and saying that because there are more 3-stars than 5-stars drafted (in this example, 30 vs 20), it means that ratings don't matter.
The fact remains it's much more likely to be drafted as a highly rated player, and more lower-rated players may be drafted simply because that pool of players is much bigger.