The problem is that the outcome is an aggregation of a lifelong process, not just the recruiting process. Trying to control the outcome is impossible, because for example there may be cultural reasons (parenting, marketing and advertising, etc...) that may result in only a fraction of a gender being interested in a field. But still we can still aim to offer equal opportunities in a bottom up manner to any candidate.
Can it be said that boys and girls have equal opportunity access to IT if girls get taught by parents or teachers or culture at large that computers are for boys? I would argue that it isn't.
So I agree with you in that simply forcing companies to hire more women is not a solution to the problem. But that does not mean that there isn't a problem, or that we can consider education, marketing and advertising, and other cultural reasons as unchangeable.
This is in fact exactly what people mean when they talk about systemic or structural inequality - there is no single point where things are going wrong, it is a whole host of different aspects of our society that together shape outcomes in a bad way.
But as we've seen with gay acceptance, change is absolutely possible, even on deeply divisive topics. And sure, it will take a long time to change the whole culture, and some people will feel deeply, sincerely, disturbed by the changes (like religious fundamentalists are feeling about gay marriage), and inequality will linger. But we do have the power to change.
Note: I'm not arguing equal outcomes in tech employment are as important as equal marriage. I'm just giving a relatively recent example of a massive cultural shift. Probably a more spent example would be the initial push for women's access to the workforce at all, but I believe that feels to distant to us.
