NU was one of the worst shooting teams in the country no matter how you cut it. They didn't shoot 3s well, but Duke didn't either. But NU also had a poor 2pt %. Effective FG %, True Shooting % -- you name it, NU was poor.
What hurt NU the most, IMO, was a lack of players who could get to the rim. Since I just read a book on advanced basketball analytics and am now an expert, the three most efficient shots are, in order, shots at the rim, corner 3s and 3s north of the FT line extended. As has been oft-discussed, midrange shots are the least efficient shots and really aren't worth taking a lot of unless you're really good at it. (I don't think advanced stats on college players are widely available, but I'd be interested to see BMacs midrange shooting % in his Jr/Sr years and wouldn't be surprised to see that it went down.)
Last season NU didn't have players who could drive and make shots at the rim at a high enough percentage to force teams to respond. Defenses could stretch and challenge floor spacers. Dererk was one of my favorite players at NU, but his 2pt % wasn't as high as it needed to be to help make up for the lack of players who can go to the rim.
A new line would open up floor spacing some, and eventually most of the players would adjust. IMO the main issue with distance shooting is form and rhythm, and extending the line will place more of a premium on that than on strength.