Lack of religious knowledge

This argument is absolutely not one! There are no criteria to fulfill or "level of faith" to achieve to accomplish the hajj. As with prayer, or the wearing of the veil, this argument is often a false pretext for the person who has not sincerely anchored in his heart the will to accomplish this worship.

For on the contrary, it is by making the causes to draw you closer to Allah that your faith will grow. If your true goal is to become a better believer, then the hajj is certainly one of the biggest causes for you to achieve this goal.

 The Prophet (alaihi salat wa salam) said:

(Allah said, "I am with my servant, according to his opinion of me, and I am with Him when He mentions me. If He mentions Himself to Himself, I will mention Him in myself, and if He mentions me in an assembly, I will mention Him in a better assembly than His own. If He approaches me with a span, I will bring him closer to him by a cubit, and if he approaches me by a cubit, I will draw near to him an armful; if he comes to me by walking, I will come to him by hastening me.”