That's a good point about those examples; they are flawed in that respect. My point was that I'd rather read an article written by an expert and held to high editorial standards than one written by a crowd of people with various levels of knowledge.
I'd also expect to learn much more uniquely valuable insight about an issue from the authors listed above, but that's a different issue.
A philosphical question I heard on Car Talk: Do two people who don't know what they're talking about know more or less than one person who doesn't know what their talking about?
Recruiting and vetting experts, and not falling into the trap of mindlessly accepting received wisdom, is tricky. So is false equivalence / false balance, and wisdom-of-crowds stuff.
Though ... some of the wisdom-of-crowds bits suggest that if you can harness the sensibilities of the many, you may end up with better results than of a single individual. I'm not entirely sold. Area of active investigation.
I'm not saying that "balance" always achieves improved results -- see the Baathist Guard of Kochinistas standing jealous watch over any article concerning the Koch brothers, Koch Industries, or the various political influencing organisations. But what Wikipedia has that Brittanica did not is a "show history" page revealing who's made what changes to a page. That is often far more revealing than the page itself.
Now: if Wikipedia would grow a pair of balls/ovaries and actually do something about rampantly partisan editors, that'd be peachy.