I think the issue might better be approached by looking at Vonnegut's intentions, and asking whether the work is successful in what it sets out to do. To suggest Vonnegut is unconcerned with character development is to suggest he isn't a skilled novelist, or doesn't have the aptitude to understand the implications of his (admittedly often experimental) stylistic choices. On some level Billy Pilgrim can't effectively be held up as an example of Vonnegut's lack of concern with character development, because the scope of Billy's portrayal extends far beyond what most 'normal' characters do in the English literary canon. In other words, because Billy is capable of living ins several different times at once, he holds awareness of the past, present and future, and tries to communicate to others that these are in fact unified parts of one moment or period of time. It's not clear why Vonnegut chose to have this character exhibit this capability, but one could assume that it is a commentary on the timelessness of war, its constant presence in human history, and its inevitable occurrence in future generations. As well, the idea that war brings out the worst in human behavior and is a perpetually cruel and unjust experience is illuminated in the death of Edward Derby, punished because takes a piece of china, only thinking it will make his wife happy. His well-intentioned act results in his death; this could be considered somewhat antithetical to character development because his death seems needless and his kindness is punished with murder. The notion of forgiveness is also at work in this novel: if Billy can manage to understand that even acts that will cause his death are inevitable, and be open to their occurrence, he can also allow himself to forgive not only his killer but the Nazis who murdered Edward. Billy finally understands that fate and destiny are inevitable, and that human choice is intimately involved in any outcome however seemingly harsh or unfair. This final understanding and epiphany (both for Billy and for the reader) represents a profound achievement in character development.