The acting in this film is cringeworthy and embarrassing.

Actually, I think it's the changes from the stage to the screen that are cringeworthy, for the most part.

If you have seen the play, the relationship between Susy and Sam is much less one-sided-- she's a willing participant in the "World's Champion Blind Woman" games, if that makes sense, and has a sense of humor, something that feels missing from the character in the film, but it really isn't Audrey Hepburn's fault. You have to see (or at least read) the play, and compare it to the film. Susy has been watered-down for the screen, as though the producer (who was Hepburn's husband, whom she divorced soon after the film was released), or some studio executive thought audiences just couldn't handle an independent blind woman, and Susy had to start out at the bottom of the self-esteem barrel at the film's beginning. She is much more matter-of-fact about her abilities and limitations in the play.

However, and oddly, the film is actually more realistic in what day-to-day rehab would be like for someone who had been blind for about a year, after being an adult with normal sight. In the play, the things Susy does to compensate, or keep track of information seem made up on the spot, and sometimes pretty far-fetched. Maybe it is supposed to pre-figure the bulb-breaking, but keeping track of phone numbers with sugar cubes is silly. A lot of the things Susy does, the way she tries to use Braille to keep track of phone numbers, types up the shopping list, looks for the pepper shaker, look like real things someone has been taught in rehab, and she does them the way someone who hasn't been blind very long would so them (I was a sign language interpreter, and I had a Deaf-blind certification, so I've been around a lot of blind people).

I think Hepburn deserves a lot of credit. I got the impression that she tried at least a little to reel in melodrama that was getting out of hand, by injecting some realism.

You'd have to say a lot more than "John Wayne/True Grit". Wayne was a superb film actor, and deserved nominations for several of his performances, including "True Grit".