Magic is odd in this show but it seems to be that there are two types of magic 1) Learned or Cursed: Cora, Regina fall into the first part and Rumple into the second. Other examples are Snow who can do magic just by having seen it as a kid. 2) An actual MAGICAL being: Emma is the only person in the Onciverse so far who simply IS magical and does not have to learn it.
I’d disagree with that premise it stands to reason that C0ra and her daughter are inherently magical to begin with and that Rumple awakened those abilities. I point to the moment when Rumple touched Regina’s face and perked up when he sensed how powerful she was. Snow doing magic was she or was she merely making use of an already magical compound i.e. squid ink. As far as Emma not having to learn, she is inherently magical yet recall the dream catcher Rumple needed to teach her how to focus her innate abilities as he had done with Cora and Regina. Consider Cora at the spinning wheel and the push Regina gave her mother through the looking glass. A & E have mentioned that some of our characters have what I believe they called the “spark.” Akin to the Star Wars universe where you have Force sensitive individuals who have the ability to feel and control the Force and train to become Jedi or Sith.
The more plausible categories would be inherently magical (Mills women & Emma) and acquired magic (Rumple)
Custodian of Graham's darts, Rumple's spindle and Robin's quiver