Why Star Trek Picard Season 2 Finale Didn't Suck (Or Did It?)
6. Whoopi Returns
Whoopi Goldberg's appearance in the finale serves two purposes. The first is to explain that yes, she did indeed remember the events of the past, telling Picard that she couldn't, of course, let him know that. This is a trope that we've seen with this character before. While it had been handled better in previous outings (see Time's Arrow) it is still a fun part of their relationship.
The second function is to give the audience, via Picard, the story of Rios's life and death. This seems intended to confirm that Rios won't return, as usually hearing how a character died is enough to pack them away in cold storage.
Does it work? The answer is yes and no. Ito Aghayre was a fantastic addition to the cast this season as a younger Guinan, even though the explanation for the aging issue was deeply unsatisfactory. Through no fault of the performers, the shadow of the aforementioned Time's Arrow loomed large over the plot, making Guinan's failure to recognise Picard stand out.
The in-universe explanation for this is sound - La Sirena travelled from an alternate future, where there had been no Enterprise-D, nor any reason to travel to San Francisco of the 19th century - and yet it rang hollow. Having Whoopi bookend the season went quite a ways to helping sell this story, even if it was muddled. Overall, her final scenes are warm and enjoyable, even if they are overshadowed by Rios's fate. It may not have been the perfect ending for Guinan, but it was far from the worst that it could have been.