If that's your take away from that article, you're wrong. The headline here at least is completely misleading.
14 players - not a big enough sample size.
Fultz actually shot 41% from 3 in college, he doesn't need to "improve" on that, just needs to
maintain that.
Of all of Philly's 4 main building blocks (Fultz, Simmons, Embiid, Saric) only 1 is a guard, and he's actually a good 3 point shooter! So what's the point of focusing on guards on who need to improve shooting?
Again the article focus on guards taken in the top 5 and top 10, but look outside of that just on the C's and we can see how untrue this is. Look how many C's have improved their 3 point shot:
Isaiah Thomas: 34.9% final college season, 36.7% career NBA, 37.9% last year.
Jae Crowder: 34.5% final college season, 34.6% career, 39.8% last year.
Al Horford: 0% in college, 34.6% career, 35.5% last year
Jaylen Brown: 29.4% in college, 34.1% so far in NBA
Kelly Olynyk: 30% in final college season, 36.8% career NBA
Half the C's have improved their 3 point shooting, and guys like Rozier, Smart, and Bradley have maintained their shooting numbers (within 1% of their final college season).
So pretty much every player on the C's has improved or maintained their 3 point shooting since their final college season.
Then even on Philly, the team that's being critiqued:
Embiid: 20% in college, 36.7% so far in NBA.
Plenty of players have increased their 3 point shooting from college to the NBA.