Accent on Youth probably had some kind of life in summer stock into the 1950's. I think the concern is that Broadway, for whatever reasons, no longer provides a venue for new works of untested value. For example, even in the late 1940's through 1960's, Broadway would countenance a Camino Real for every Cat on a Hot Tin Roof. Broadway was friendlier to new playwrights and was willing to give them a second chance -- think Arthur Miller, who started with Man Who Had All the Luck, then gave Broadway All My Sons and Death of a Salesman. And forget about the sort of thing that was going on in the 1920's, when Eugene O'Neill had a big flop (both commercially and artistically) for every hit and producers continued to back him.
I feel that, with the influx of the tourist trade and more ready access to the Broadway stage, there has been a dumbing down to satisfy the broadest audience possible. Taking a chance on a new playwright no longer seems to be a viable option.
BroadwayEd