The fact that fur is growing but growing slowly is what I understand your concern is today. Since it is winter in the northern hemisphere, the winter coats go into a resting phase and soon as spring approaches, the hair will begin to be shed again. I would imagine that the kitty will soon grow new hair, although it only grows about 1/4 of an inch a month when it is growing season. Also, some kitties have issues with thyroid gland disease. I don't think this is the case, since there is "fuzz" growing. If there were no hair, then I would be concerned about that. If your kitty is eating, drinking, and doing well otherwise, it probably is just that the hair is in its resting phase.
I hope this is helpful. Please push ACCEPT and thanks!