Except, and this has already been pointed out in this thread, it wasn't Roddenberry's fault. Roddenberry had fuck-all authority over Star Trek after The Motion Picture.
Ok so why did they listen to him, then ?
, that's the whole point.
Meyer wanted Alley to return as Saavik. She was busy with Cheers
and she would have cost too much anyway, as the film was on a very tight budget. He did not
want Curtis. So, faced with having a third actress play Saavik or creating a new character, he went with a new character.