Fair enough. But towards the original point, dismissing a solution to a problem because of the relevant campaigning, and not the relevant changes seems like a pretty poor argument. Additionally, you could also take my statement as meaning, "if the campaigning isn't succeeding, perhaps trying to change the message will help". Which, encouraging STEM for all children, would be a new message that would also likely increase the number of women in STEM (eventually). This is actually a pretty common shift in the "women in STEM" movements as of late.

As a counter argument: There has been lots of campaigning on fixing the problem of limited numbers of women in STEM, but relatively few changes to the media portrayal of women in STEM or education of children to fix the problem. Perhaps more importantly, a vast number of STEM fields are in high demand, and our education system seems to be poorly equipped at encouraging students (in general) to enter (any) STEM field. So perhaps we can hit two birds with one stone and change how we teach STEM to be a more integral part of school, like the original post suggested with a relatively provocative title.