A.R. Gurney, who died in June 2017, was prolific to the end. Like Verdi, Henry James, and Philip Roth (a recently deceased contemporary of Gurney’s), this urbane playwright exercised robust creative powers far beyond customary retirement age. Judging by the number of high-profile revivals since his death (most notably last season’s superb Off-Broadway production of Later Life), Gurney’s wit and insight are still integral to American drama.