Denny, I didn’t elaborate because Emw mostly did so for me. But since you asked, I will do so as well. Let’s start with your examples.
The allowed value for the “country” property should not be “goat cheese”. The allowed values should be those items that contain the statement “instance of: country”. And you’ll notice that this allows ambiguity, because even though Kosovo is not a country according to Serbia, it is a country according to some other countries. Since Wikidata is not about the truth, but about statements and their sources, we can record that a certain country stated that Kosovo is a country, just as we can also record that Serbia stated that Kosovo is a region within Serbia. And yes, Wikidata would also need built-in “instance of” and “subclass of” properties.
Does every country have a capital city? Emw mentioned Nauru, which doesn’t. Well, Wikidata already covers that – the “no value” special property value.
Why isn’t it sensible to restrict the domains of properties as well as their ranges? The domain of “capital city” should be restricted to those items that are instances of countries (or countries union administrative divisions, not sure). That is, after all, part of the semantics of the “capital city” concept–why shouldn’t we be able to capture those semantics?
Can authorship apply to a song? I haven’t yet heard the argument that it can’t. But if someone claims it can’t, and others claim it can, obviously they have different definitions of the concept of authorship. And that is fine, because those different definitions can be captured by different properties. What’s wrong with that?
What’s wrong with ontology engineering? You said you think that it can get stuck in a fundamentally unresolvable situation, how and why?
What I’m mainly disappointed about is that your opinion in the article, and thus the design of Wikidata, is presented matter-of-factly, and not as an invitation to a discussion. Don’t you think anyone beyond the Wikidata team should have some input regarding these matters?