I'll say it again, the biggest issue is that he's the most common archetype, easiest type of player to find in the league.
Shooting guards who don't do anything other than score aren't that valuable today, even if they're efficent, consistent 20ppg scorers.
Unless you're a 25+ a night player, you better either defend or create on high level, days of pure scorers are long gone if we're talking average starters.
No contender in the league starts a pure shooting guard right now.
Mitc is a ballhandler, averages almost 5 assists and is one of those 25+ whenever it's needed scorers.
If we assume Castle/Wemby is the core, we need two 3-D players for the starting lineup and a legit triple threat who can score with ease and create for others.
Champ is the placeholder 3-D guy. Who knows, at this rate he might take another leap and become a legit starter.
CP3 is the temporary creator solution.
Obviously Jeremy is starting ahead of Castle, but it's going to be really hard to incorporate both in the starting lineup if they don't develop reliable jumpshots and Castle obviously has a higher ceiling.
Devin is just redundant. It's his 5th season, even if he becomes the best realistic version of himself, he's still a common player.