It's utterly baffling to me to see them specifically call out editor gender disparity as an issue and then seriously suggest that a ui redesign will fix this.
The issue isn't the software, it's people. People being allowed to be terrible to other people. People pushing euro/american-centric, white-centric, male-centric viewpoints. People creating a feedback loop of intolerance by making the place only habitable by the intolerant.
There is some evidence (I believe from a commissioned study) that the current interface disproportionately filters out non-technical would-be editors from contributing, because of its heavy use of markup in a plaintext editing field. Stuff like:
<ref name="citekey">{{cite book | title = ... }}</ref>
is impenetrable to some would-be editors, especially when it starts getting more complex and nested. Even as a long-time editor with a CS background, I sometimes find it hard to skim past big blocks of markup to find what I want to edit, and it's easy to screw things up and end up with unclosed ref tags and that kind of thing. To someone who doesn't even know what an "unclosed tag" is (most people), I can only imagine it'd be many times more confusing.
Since people with technical backgrounds are disproportionately male, it could be a contributing factor to the gender disparity. Hardly the only one, but a WYSIWYG editor may at least broaden the population being drawn from.
If the site were more user-friendly, it would be easier to use for people who don't understand the initial complexities of Wikipedia. One of the contributors on that page wrote against a redesign because they don't want to have to re-learn how to use the site, insinuating that the initial learning curve was rough for someone who is an editor, not a web person.
The redesign should include better promotion for the site/make people aware of the contribution process just as much as it should focus on the content management and discussion portions.
Those -centric are problems, but there are others too; in a great many articles people with specific interests tend to form cliques that rigidly enforce certain viewpoints, not objective consensus or broader cultural consensus, just what those users insist should be seen.
Those interest cliques are very often nothing to do with being euro-centric or male-centric.
The issue isn't the software, it's people. People being allowed to be terrible to other people. People pushing euro/american-centric, white-centric, male-centric viewpoints. People creating a feedback loop of intolerance by making the place only habitable by the intolerant.
You can't graphic design these problems away.