I'm with Sephirah's suggestion lower down this thread that 'it's not can't, it's won't.'
Even on Susan's there are people using the phrase 'biological sex' as if it is a firm definition, but it is not, and explaining why it can't be involves more understanding of genetics and biochemistry than someone without the appropriate background can possibly hope to understand. The moment you start talking about stuff like 5α-reductase type 2 enzyme deficiency, people's eyes glaze over and for good reason.
I've a good grasp of why you can't define biological sex and I'm a good communicator, but while it's relatively easy to shatter most people's idea that there could be such a thing as biological sex by highlighting all the edge cases nature throws up, and why healthcare organisations from the UN downward have split sex and gender to account for that, that's not the issue, I think.
To me, the art of reducing discrimination of any sort has always belonged in the fields of compassion and familiarity. There's a lot to learn from the way the gay community patiently educated and recruited champions to make the general public aware that they were just like everyone else. They conducted that campaign on many fronts and although it took decades, they won in the end because they stayed focused.
We've won our campaign too, more or less, with Gen Z and late millennials. We have high profile trans musicians out there making our case every time they pick up a mic. And sure, we also have boomers fighting a rearguard action against any change from the status quo, but they'll only be around for so long.