Agreed. I haven't seen a production in a long time, but my recollection is that there's nothing wrong with ARSENIC AND OLD LACE that would require changing or updating a single word.
What might be interesting is if someone wrote a play that was a contemporary response to ARSENIC. Who would these characters be in the 21st Century? Does the advent of technology affect the plot at all or do people still fall through the cracks of society, despite social media and limitless ways to be in touch? Would the mental health concerns of one of the characters be treated differently? Would the character who's a theatre critic in the original still have a job at all? Would he be in electronic media or might he be holding out at some publication trying to single-handedly cover as much theatre in New York as possible?
What if THE GOLDEN GIRLS were killers?
I have no idea what the rights situation might be or if the Kesselring estate would have to sign off on such a thing. Maybe it depends on how far the new play would stray from the original. But this is something that I wish more writers would do and more producers would commission, rather than endlessly updating existing properties from another era. We don't need another KISS ME KATE with another rewritten book. We certainly don't need another take on ANYTHING GOES or ANNIE GET YOUR GUN.