He looks good on the fourth line playing a fourth line game for the time being. He's out there when the fourth line is out there. Different prospects need to develop different ways. Maybe CK isn't the kind of guy who can just jump into the top 6. Maybe he needs to ease himself in, start playing a hard grinding game, then when he gets that down, move up a line and work on providing support offense, then when he gets that, move him up another line and work on providing more consistent offense.
Nobody here knows more about this player than the actual coach of the Rangers does. Not you, not me, not the chorus of armchair coaches.