A lot of adjustments are made at the pro level. But the Bulls problem, is that they play full on defense in practice to master Thibs craft, which has shaken up players and thrown guys off rhythm. Korver's % dropped as a Bull, so did Belinelli, MDJ, Troy Murphy, Tony Snell, and every other player in the same position. The only argument for guys that didn't see much of a change were shooters that are primary ball handlers.
If the Bulls bring in a legit shooting coach, then you can take the existing players and improve their shot %. Not only does it benefit inexperienced rookies, but it benefits veterans. Every team that has brought in a shooting specialist, has taken their teams from being in the bottom 10 to the top 10. That is how much of an impact a shooting coach has made. And at some point, every team will eat up every worthwhile shooting coach, so IMO, it's better to get someone sooner than later. Only a handful of teams have one now.