I agree. When Mrs. Patrick Campbell (at 55 years of age) reprised her role as Eliza in a 1920 London revival of Pygmalion, I doubt if anyone complained. However, I'm awfully glad Anthony Asquith went with Wendy Hiller (she was 26) in the '38 film version (over Shaw's suggestion to cast Mrs. Pat who was 73 at the time). I'm pretty sure Leslie Howard agreed with that decision.
I wonder if Elaine Stritch had Campbell in mind, when she wisely remarked "It's not the work that gets you; it's the stairs". Close should ponder that sentiment. The staircase in Desmond's mansion is a mighty tough climb.