Yes...fairy tales get changed every time they come to stage, screen or the written word. Sleeping Beauty is no different. In some of the old versions of the written story - which was spun several ways - the Sleeping Beauty is raped, for instance; I don't think anyone minds the fact that they've changed that.
And the ballet of Sleeping Beauty is different from the 1950s film, which is different than some other gazillion film versions, which are different from Maleficent. It is just one more interpretation, and I think it's up to the viewer to decide which one they like.
Oddly enough, confirming that Maleficent is a fairy brings it back to the original French story, which indeed has a fairy, who is disgruntled about being overlooked and not invited to the party, who curses the baby.