"College is unquestionably more rigorous today." This is likely true at the high-end. But the vast majority of college students are not at the high-end. At the mean, universities have to mop-up after a dysfunctional K-12 establishment based on self-esteem and social-promotion. Remedial reading, writing, and mathematics are common at second- and third-tier universities. The scope of "special needs" has been broadened to include customers who are incapable of producing college-level coursework.

To ensure that students who elect to pursue a rigorous education are not penalized relative to those who do not so choose, grades at those institutions have been inflated to meaningless extent.

The educational industrial complex is geared toward growth. Effectively serving that market requires lower baseline standards and less meaningful quality metrics within the serviced population. Certainly the market is consuming more educational product than in the early 60s, but whether this produces a better educated populace is less obvious--unless "better educated" is defined to mean "consumed more educational product."

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"in the early 60s there was a massive gender gap in college attendance" As an aside, today's gender gap is the opposite: colleges attract fewer males than females. If you consider graduation and 4-year graduation rates, the gap is greater and growing faster. I don't know that this marketing failure says anything about the quality of education though.