Bill, I have been in the workforce just a bit longer than you, so our views of history are probably pretty similar. My experience has been that Title 9 did not magically eliminate prejudicial behaviors - they persisted at slowly diminishing levels, even in government, with some companies doing better and some not nearly as well.
So, my point is that there are still some out there who are prejudiced and act on their prejudices, perhaps in less easily identified and prosecuted manners than before.
But, I also doubt that accounts for the less than 50% female composition of the engineering ranks. Males and females are given equal rights in the U.S., but clearly are not physiologically or psychologically identical creatures. Not even all males or all females are physiologically and psychologically identical to their particular sexual chromosomes.
The point is that each individual should get an equal chance to do what they want to do. Quotas that assume identical aptitudes and desires for all individuals are actually just as discriminatory as assumptions of unequal aptitudes and desires based on non-relevant parameters for the specific tasks.
And, note that I said non-relevant parameters. Obviously, some parameters are relevant for some specific tasks. But, from an engineering job perspective, those are not really correlated with easily observed physical traits such as sex, size, etc, A "big brawny man" is not necessarily going to be a better (or worse) engineer than a "little girl". Same goes for pretty/hansom vs plain/ugly, etc. etc.
Although there seem to be differences in the averages for various attributes for various identifiable groups, the variances within those groups are too large to allow predictions of who is better between 2 individuals from different groups. But, the differences in the averages may well account for different fractionation of the work force in a particular field vs group identities.