I see Jack as a more athletic Lance Whitnall. Whitnall was very smart for a footballer (off field, not so much) and he made a career out of outsmarting his opponent even though he had no athletic credibility at all. But when the little bit of athleticism he had disappeared, even the defenders who had low footy IQ but great athleticism could beat him.
Jack's had moments over the last couple of years where he just can't get away. Yes our forward delivery has been poor, but he can't separate from some opponents. He has the ability to get away from some still, and could until now take a decent mark. But if he loses half a step and/or has no leap left, he could become an ordinary player quickly.
I hope that's at least 12 months away, because I love watching him up and about.