I think people in this world generally do learn the other spells within their elemental affinity, but there's pnly so much a spell can do at a base level. By customizing it, they can expand what a spell can do.
Remember that up until this point, Kunon was only taught 2 basic spells, and...
It's pretty obvious that she has her memories. She just enjoys toying with Ooma.
Plus I think there's more value in a relationship built on the now and not a past life.
I would argue those ideas are still present even late into the series. Like Minami meeting Akira at the cafe in girl form, saying "It's just my preference". Or in the second to last chapter on the date with Karin thinking "Maybe I should have come as a girl so we could both be in high spirits"
Ironically, I think the original did engage with the gender themes. It just never got to see them through. I'm glad to see this one try to bring those themes to their conclusion.
It's hard to fight with Magenta like that. At the end of the day, Utena's goal isn't to win, it's to make the magical girls look good. And depraved Magenta is not a good look.