So, I think the results of this poll deserve an analysis to some degree. It was very enriching to talk, exchange and read ideas and takes from other "Cinderella academics" and theorists.
@visionsofloveandmagic mentioned in the comments a book on symbols mentioning the Cinderella story falling under the archetype of a maiden being rescued from imprisonment by a prince. I don't necessarily agree with this, but even if it were true this would be more of a structural description, akin to the Aarne-Thompson-Uther Index for folktales, which categorizes structures more than themes. Even then most myths and fairy tales tend to fall under several categories of the index, including Cinderella.
The most voted option by far (with an astounding 50% total) was that it's mostly a story about keeping kindness and hope despite things looking grimm (no pun intended). I think this is directly related to how both Disney versions shaped the collective consciousness about the Cinderella story, due to them being probably the most popular versions worldwide, besides the Grimm and Perrault versions. Both "A Dream is a Wish your Heart Makes" and the iconic "Have Courage and Be Kind" mantra, have become staples of the Cinderella story. And I do believe these two elements are very core to the story, but there's an argument to be made that wasn't always the case in all versions (especially older versions), but most of them do feature those belief systems heavily.
The second most voted option was the one I personally voted for: regaining identity and self. There was a post I made here a while ago where that was kind of the core theme of the Cinderella story for me. Regaining implies losing first and that's encoded in almost all versions of the story. The idea of identity tends to not be mentioned frequently when analyzing the story and it is crucial, down to the title of the story itself. What's more, this for me is directly related to the theme of grief, which is not only about her parents, but also her previous life, her original name and even how she looks, which is also an identitary notion.
Then we had a tie for third place, between "Family Drama" and "Being rewarded for being good". The family drama stuff I also believe to be central to the story, as most of it involves her parents, the stepmother and stepsisters. You could also argue that her marrying in the end also ties into this. On the other hand, I included the option of "Being rewarded for being good" mostly because Perrault himself included it in an end note at the end of his written version. That being said I don't believe that's always an element in the story, especially the ones taking after the Grimm's version, which I would argue has a very different set of values in that sense (which personally I love, as I think the "rewarding" notion can make her kindness feel transactional or christian in a very conservative way).
I also found pleasantly surprising that the second least voted option was romance, because I think we are starting to understand collectively that this is not a romance story, despite Hollywood, some adaptations and public discourse (at times) trying to convince us other ways for many decades. But just like in many other stories, romance exists within the story but it's not at the center of it. The prince, as I mentioned before, is more an element of family than romance.
Now, @princesssarisa whose knowledge of the story I also trust a lot, considered the element that shines through the most and more consistently in almost every version is finding one's inner or true beauty and/or place in the world. I definitely see why and I agree it is virtually present in every version, especially because another element I believe to be at the center of the story is "otherness" and how Cinderella represents both the notion of otherness itself and how otherness deserves a place despite the world trying to keep it hidden.
But I will say, the most compelling argument, for me, came from @ariel-seagull-wings whose opinion I also value a lot. They mentioned that the defining element is actually class commentary. The other elements can be found (even many of them at the same time) in other folk and fairy tales. But the element of class is distinctively Cinderella, at least in the genre of fairy tales. She is a servant, she is working class, they look down upon her because of this, she wears rags, she doesn't have a bed in many versions. Other versions like Ever After, The Slipper and the Rose or Bridgerton put in evidence how much more difficult that makes the resolution of the story. Even the 2015 Disney's Cinderella makes a point of this (especially if you take in account some deleted scenes).
So, in conclusion, of course it's a mix of many of these themes. But if you were to compose the main ones, then definitely the class element, finding a place in the world, grieving and regaining identity, family drama and keeping hope and kindness are the main ingredients for the archetype which each version creates from.
