The documentation does need work, but it's hard to find people volunteering to do it (although a few people do contribute to the docs too and this is something that is always very much appreciated). Any concrete suggestions for improvements are welcome as reports on https://trac.wxwidgets.org/newticket and, as you might have already realized by now, PRs to the docs on https://github.com/wxWidgets/wxWidgets/pulls are even more so.
Finally, asking questions (on the forum, users mailing list or SO) seems to work pretty well for most people.
And yeah, I hear you on the people issue... open source is sometimes a thankless job. Overall though, great job on wxWidgets so far - I really do think it's an underappreciated project.
The great thing is you can just look at the source if there's any confusion. One issue is the mildly broken nature of the macOS version (odd bugs now and then) but that's because Apple keeps changing things. It is significantly better than it was 5 years ago!
Try reading other documentation like MFC and you'll appreciate the wxWidgets documentation...
Cocoa/AppKit rarely change, and it's often one of the bigger complaints with it. Big Sur is probably the most radical version change set in years, but to say Apple "keeps changing things" for Cocoa/AppKit is not really correct.
Also, if it's not clear, I _do_ read other documentation. I still think wxWidgets needs work, and one of the devs even admitted as much in their response to me.
I think it probably gets a bad rep when compared to "modern" UI development frameworks, however this thing is still trucking along all these years later. I'm not sure I'll need to touch 3.1.5, but it's just really cool to see it still being worked on.
I think the biggest thing the project needs though though is... documentation. Or maybe it has it, but needs some serious SEO work to make it better accessible? So much of my time was spent trying to figure out what specific feature flags meant, whether they were still valid, and so on. I've done Cocoa development for years, so I'm used to outdated/old documentation, but with wxWidgets it just felt... harder to find the right stuff. Maybe because the userbase is smaller in comparison?