At its simplest, the point is that much of programming language design is done with a masculine perspective that values technical excellence and very little feminine perspective that focuses more on social impact. Most, including myself, have a knee-jerk reaction to dismiss this argument since at first glance it appears to trade off something known useful for something that's usually little else than a buzzword, but upon further reflection the argument is sensible.
The theme of forsaking technological perfectionism in favor of reaching whatever end goal you have set is widely circulated on this forum and generally agreed with. Those of us that work as software engineers know that impact of your work is always valued more than the implementation or technical details. It's thus reasonable that when building programming languages, the needs and experience of the users should be considered. Not override everything else, but be factored into the equation.
I know if I were to write a programming language I'd probably focus on pushing the boundaries of what's technologically possible, because I find it fun and interesting. But I would have to agree that even if I did succeed in doing so, the actual impact of my work would probably be lower than that of Hedy - the author's language. Hedy is not novel technologically, but the fact that it makes it meaningfully easier to learn programming for significant numbers of people is real, undeniable impact.
Lastly, I want to note that the author's argument for underrepresentation of women in PL cannot be reduced to "those nasty men are keeping us out". Humans are tribal and any group of humans is bound to form complex social structures. Those are going to affect different people in different ways, linked paper investigates the effect on those structures on specifically women because the topic is close to the author. Whether you care about low numbers of women in PL design or not, the dynamics that have led to that being the case are worth investigating and are quite interesting on their own.