The Manhattan Theater Club production that opened on Tuesday, starring the rom-dram charmer Rachel McAdams, confirms that earlier diagnosis. But Herzog, whose Broadway adaptation of “An Enemy of the People” is running a few blocks away, is not interested in locking down meaning. Like all great plays, “Mary Jane” catches light from different directions at different times, revealing different ideas. On the other side of the worst of Covid, “Mary Jane” feels less like a parent’s cry for more life than an inquest into the meaning of death.