What's the problem, I see what you are writing and you should be very happy about him leaving then?
Of course he will improve his game but not playing for the New York Rangers obviously.
One thing I really hate is when fans writing degrading things about players leaving.
Perhaps he didn't fit in this setup of Rangers and probably strongly felt management and coaches losing faith him in. He is a young guy but only one career in the NHL. A situation where management and coaches not believing in you is awful/terrible, losing faith and hope in you, then you should leave the team and prove them wrong. He is doing the right thing, no question about it. Rangers sometimes suffering from the Maple Leafs syndrome, lacking of patience developing talents.