Hecate is most definitly a crone goddess. People see the word crone and immediately think old, ugly woman. This is not a factual repreentation, rather a demonstration of the limits of language.
I am inclined to believe the idea of a triple goddess is a Wiccan invention. A lot of Wiccans believe there is only one goddess who manifests herself in different ways; maiden, mother, and crone.
Hecate is not a crone. Hecate is her own goddess, she is Hecate. Goddess of magick, crossroads (choices), and has a hand in the knowledge of death.
In the belief of a triple goddess, if we had to assign a title to Hecate (maien, mother, or crone) she would get the crone title due to her association with magick, wisdom, and death.
But if we abandon the titles and us worship goddesses as separate deities, as the ancient Greeks did, the problem is erradicated.
Not to mention, when it comes to deities it i very sujective, our own perception, limitations, and expectations get in the way. My image of Hecate will not be the same as your image of her.