I'm wondering, not having followed Ryan's comments, has she ever discussed what SHE thought of Seven's having to repeat lessons?
IMO, the character of Seven was good because of the writing of her and Ryan's performance. Though she seemed to repeat a number of lessons, she was allowed to progress and grow. An effort was made by the writing staff, or Paramount, to let an actress act. Ditto for Picardo, though towards the end of the show, I found his character more grating.
Mulgrew was good at acting, but the writing of her character became so inconsistent--what could she do about that? Likely not much. Some other actors (O'Neil and Dawson) became more interested in directing, so they may not have minded their characters being lessened. Beltran, I won't get into here to much. I believe he was capable of more but little was written for him. Wang was less experienced as an actor, but did a decent job with what he was given.