...but that was the ending she wanted before, when she thought there was never going to be anything more to her life, before she knew how amazing she could be.

Yes... you've put your finger on what it was that continues to bother me about Donna's ending. It's not a bad ending, but it represents a complete loss of everything she gained while travelling in the TARDIS, and all the ways she changed. She's been forcibly reset to who she was before we met her in The Runaway Bride, and I can't help feeling that's terribly sad.