Smith barely had a chance to do anything, Yeoman Colt would have been better. And what Melekon said.
I thought the addiction problems began after being fired in such a way and were promoted after the fact as why she was fired. You know, like why the network couldn't have a female second in command.
They sure didn't fire Leonard Nimoy because of his addiction problems. Of course I'm not saying they should have, nor am I saying Grace Whitney was as good and actor as Nimoy, either.
Nimoy wasn't as addicted as Whitney (yet, so I believe) or as addicted as Roddenberry would be in the coming years.