That is awful and unacceptable.
Awful, yes. But its clearly acceptable, because he is a top 5 PG in this league.
I don’t think its acceptable, when you are making so much money, you are expected to work a lot harder to improve your game. I don’t get the impression the Rondo works hard on his shot.
What makes you think that? There has been a number of reports saying that Rondo works on his free throws daily from Ainge, Cedric Maxwell, ect. It may not translate in the games, but that doesn't mean he hasn't practiced them. I think it's more mental than anything right now.
From what I've read about muscle memory and training for something like free throws, I have little doubt that either
a. Rondo is not spending enough time working on ft's or
b. He is spending time working on ft's but practicing wrong.
If there's a flaw in your delivery, it doesn't matter how much you practice, but any coordinated athlete, if they accepted appropriate coaching, and were willing to stick to the coach's changes, should easily shoot 75% on ft's.
Now this next bit is very unfair, but I could easily see Rondo being too stubborn to accept coaching on free throws and changing his formm/delivery, and just practicing and relying on what "feels right" or "feels natural." But what he's doing now isn't working, he needs to change.
Look at Pierce. He's changed his delivery, and at first it looked weird as hell, but he's gotten much better and consistent since the change.