I have a question: what do people want from a mystic class? What role would a mystic play in a party?

As someone that has only ever played 5e D&D, I've only read a bit about how psionics worked in previous additions (as far as I understand it, as sort of a point-based alternate casting system). It seems to me that the Monk and the new UA subclasses work flavor-wise as psionics, and I suppose that the alternate spell points system presented in the 5e DMG could be used to represent the traditional point-based casting of a psionic character.