All the characters in Caroline or Change are cis. Let's not go automatically demonizing or dismissing cis people, male or otherwise, with some automatic assumption of their lack of ability to think or write outside of their own specific experience as whatever mix of gender and race they are. Kushner's cis-ness seems to have nothing to do with any criticisms or speculation of criticisms of his work in Caroline. Not being female, maaaaybe, but people born as female and continue to identify as female are also very much cis.
Apologies if I misunderstood your meaning, but it's all to popular a default these days to throw "cis" in when discussing the potential limits of ability, perspective or appropriateness of a creative person, and in this case (as with most, since trans stories and stories utilizing a trans perspective are still relatively uncommon despite them being massively more common than ever before).