Thanks for this comparison! As a bit of a Semantic MediaWiki advocate these days, I would to like to respond just briefly to a couple of points:
> Dependency management is complicated for semantic modules.
Composer is used these days to take care of dependencies.
> URLs are machine-friendly at best. MediaWiki is the only software that doesn’t form lowercase, dashed words in URLs. Visually distracting when viewing an article on a MediaWiki site. Workarounds break some linking functionality.
Not quite sure what’s “visually distracting” about not having “lowercase, dashed words in URLs”, although this, too, is possible. URLs simply reflect the page title. Incidentally, if you require visible labels to be different from page titles, there’s the excellent DisplayTitle extension to take care of this.
> Themes in MediaWiki are not great. There is a design aesthetic to wiki dictated by Wikipedia, and we might just be stuck with it. Alternatives ask that content be changed in such a way that one can’t easily switch between skins, and that is even worst.
This used to be a big turnoff (you could recognise the familiar retro look of a MediaWiki site from miles away), but since the introduction of Bootstrap/Foundation-based skins (such as Chameleon), a lot has become possible.
> MediaWiki markup is complicated to do normal things, and alternatives require additional server resources.
As anonymous editing is important to the Wikimedia Foundation, it’s not difficult to see why the use of inline scripts and some forms of html is disallowed by default. But “raw html” can be enabled and the Widget extension offers a perfectly adequate alternative — installation is straightforward.
> Portability is an issue. One can’t copy and paste into a blog post, which is how it should work.
If this is about preserving the features of the original markup in say, a .docx file, I think there’s a limit to how much you would really want to preserve — basic markup such as bold and italic, yes, but macro’s?
Cheers, Dennis (Wikibase Solutions — www.wikibase.nl).