My apologize for unveiling the CA of Alli, doesn't know about that..
I play online's tournaments, so consider the CA cause it's the only thing that matter..
You're right bigpapa, probably only Ziyech is a good comparison for role (cc's with offensive duty) and age (24).
Now thinking about a better comparison we can take Sergej Milinkovic-Savic from SS Lazio. I'm italian so observed very well the player, and he's pretty good.. potentially he could be one of the best offensive midfielder in the world in the future but.... last year he had the first very good season of his career, scoring 7 and serving 10 assists. He also didn't play in European competitions, 0 caps with Serbia.. I'll not say if his CA is higher or lower then Alli, it's not this the point.. but italian researcher increased his CA a lot.
Alli played in the BPL, maybe the must difficult league in the world.. he scored 18 goals, served 9 assists and bring Tottenham (together with Kane, Eriksen ecc..) at the 2nd place. Not a good season in Champions/Europa League? Yes, as all Tottenham players..
In my opinion, he's probably one of the best interpreter of the role that Pochettino gives him. Already at 21!
And this is not reflected in his CA, that was incremented only of 3 points..
Sorry for my bad english.. hope it's understandable..