I think that many people (not only men) believed that having women's rights legally enshrined would be all that was required. You have the same rights now, so surely any failures must be because you're doing something wrong (like the whole bs lean-in idea).
The reality has proven to be far more difficult. True equality requires a fundamental shift in how society thinks about women, which requires effort from each individual.
Discovering and changing your internalised biases is hard work, the kind people often need therapy for. Having to do that when it means recognising and acknowledging your personal privilege is even harder. Add in pressure to fit in with your peers and it can quickly become something you'd rather just avoid. That's a very normal human reaction. In order to overcome this, women have had to basically scream each message from the rooftops until it finally sank in, and the internal changes started.
However, screaming things from rooftops means some people will feel bombarded, while others are likely exhausted, feeling like "I changed thinking x and y, what more do you want from me? I'm doing my best, why isn't it enough?", and, again, respond by avoiding the topic.
Tldr, it's hard work for no immediate benefit to the person doing the work, possibly even negative consequences socially. Who wouldn't want to avoid that? Also some people are exhausted from the work they've already done.