Say what you want about his play style since everyone has his/her own preferences, but his commitment, loyalty, intelligence and professionalism are through the roof. Why is he a Captain? Because of these qualities. The Kings did not fail to win more because Kopi was made Captain, they failed to win more because GMs failed to build a good enough roster in the post Cup era.
It will be extremely sad when he retires, but you can't hold it against him for the reasons for retirement even if his body could take a couple more years...