It might be that your wife simply has little or no desire for sex, and nothing will ever change that. Or it might be that your wife has never learned out to take pleasure in sex. Or that she can't relax enough to enjoy it. Or that she has misconceptions about it. No one on this board can answer those questions for you.
It is possible that a good sex therapist could help you. But that will only work if your wife is motivated to go and to be an enthusiastic parctipant.
