I know how it is to get a hard reject, it hurts but the reviewer is right, your theme looks outdated and it has been done too many times before, you can find similar themes like yours on themeforest so many of them that you can’t tell the difference anymore.
I think you need to develop/ design something unique and original it is the only way you will get approved to themeforest, this marketplace is very strict and restrictive the best of the best so you will have to create something that fits into this patern.
I am sorr if I seam harsh but this is the reality.
I am sure someone else will give you some advices what you could do to improve the theme but I don’t think it will be approved with the current concept.