Kanter would have been ruined had Corbin not brought him along at a pace commensurate with his growing abilities. Look how timid he is this season and imagine how much worse he would have been two season ago.
Your playing time concept is fools gold.
You hit on the whole point of this topic. Kanter's in his 3rd NBA season and still timid as hell. All that sitting on the bench didn't do much to shake that out of him.
There is the crux of the debate. Expressed in the question, why is Kanter being so timid? Here are some possible causes/conclusions:
* Not enough PT early on
* His development is perfect and he would be even more timid if he had had more PT early on
* His injury has made him gun-shy
* He is naturally timid and will never overcome it, or only with great difficulty
* He is not engaged and doesn't care about winning, nothing to do with timidity at all
* He is not engaged because he is discouraged about losing so much this season
* He really doesn't like basketball (John Amaechi Syndrome)
So I think it is very hard to say with certainty which of those it is, or maybe something else. Maybe he has another condition and needs a good clapping to get it fixed.
This debate is philosophical and so we will likely never reach a conclusion. Some feel that bringing a player along slowly is the best way, others feel that putting their feet to the fire is the best way, still others feel a balanced approach is better, and yet others, myself included, think that it should be different for each player and that there is no magic formula you can just apply to everyone out of hand.