Man, I cannot deny and submit to the reality of wordpress dominance. That said have you ever poked at wordpress plugins code ? I won't name the one I read but it was a catastrophy. And not in a pedantic purist sense, real catastrophy, dead code everywhere, while loops 8 screens long, copy pasted above each others. I think it was #2 most downloaded at the time.
The code is crap. Wordpress is crap. It's unsafe, open-to-hackers crap. The plugins are crap.
But it solves the problem users want solved. It's lego-level blog assembly, which is as technical as many users want to get. A much "better" system - maybe a nice type-safe Haskell static HTML templater with a command line build system - wouldn't.
Flipping this around, from the user's POV, "I wrote some code that almost does Thing X" is not a solution - it's just some code that doesn't quite do the job.
It's nice that it uses functional programming or formal methods or $shiny_language or ML or whatever. But if it doesn't do the job, it doesn't solve the problem.
I don't agree with the analysis. It's mostly that mainstream life floats on ambiguity and undefined contexts. Wordpress does some things perfect for users but then bug or leak or plugin conflicts happen. While other platform may have solved this prior but it's a problem that users didn't anticipate so they didn't value it.
In all likelihood, because the people maintaining Wordpress are the people who created it in the first place, and they don't know any better.
Why did PHP apps suffer from SQL injection attacks, long after PHP supported prepared statements? Why do Java apps often have ridiculous classes like AbstractSingletonThingFactoryFactory? Why does the Javascript community (still) promulgate useless leftpad-like packages? Why do Ruby apps often end up so heavily metaprogrammed that you can't trust any line of code to do what it says?
Cultures are hard to change. The people that are turned off by Wordpress' programming style probably pick other projects and other communities. Lots of the folks working on Wordpress probably cut their teeth in that codebase. They might not like it and they might realize there are better ways, but there probably isn't a critical mass of them that share a vision out of the morass.
Personally, I took one brief look under the covers of Wordpress and immediately decided to avoid it.
There's such a thing as taking the backwards compatibility meme too far though. You can't keep catering to those that drag their feet. Release an update and say that the legacy will no longer be supported a year from now.