Meh...we're talking about mostly undrafted/second round pick guys who are being inserted into a well established rotation where there's not enough shots and touches to go around in the first place. It doesn't surprise me that it happens. It's one thing to step in and play 3 minutes where you're likely to blow out the team because your teammates are way better. Completely different if there's no pressure to win, your team has to play you by default, and/or there's not enough people to handle the ball and take shots.
In almost every game situation where a young player has played, it's most helpful to the team to take a backseat. The talent difference between the guys in rotation and out of rotation is huge,. JC might be the worst player in our top 9, and he was 6MOY last year. Forrest is way above average for a two-way guy, but when he steps onto the court and JC is the next worst teammate of course he's going to be hesitant. Don't think it has much to do with Quin. More to do with the team/game situation that is available.
I generally think Quin has done a great job over the years of building up and developing guys on the fringes despite being a winning team, but this roster in particular is just insane in terms of talent. But with that in mind, maybe it does give credence to the idea that the guys we have simply aren't that good.