I can't agree with your views. They are not overly dependent on Rashid Khan. His performance during the recently concluded tri series in Bangladesh was brilliant, but that doesn't mean that the other players didn't played well. Afghanistan is a well balanced team and especially in the spin department they have plenty of options. Mujeeb Ur Rahman Zadran is just 18 years old, but he has emerged as a world class spinner capable of troubling the best batsmen in the world.
The only department where they seems to be struggling is with the middle order and lower middle order batting. In many of the matches, their openers (Hazratullah Zazai and Rahmanullah Gurbaz) were able to give them good starts, but the middle order collapsed and in the end they lost the matches due to it. This is an area where they need reinforcement.
But just check the age of their star players. Don't forget that Rashid is just 21 years old. Most of the team is composed of teenagers and those in their early 20s. They have a very bright future ahead.