I'm not really sure exactly what claim about crowdsourcing you are calling false. If the claim is, crowdsourcing makes all wikipedia articles excellent, then it is trivially false. If the claim is, crowdsourcing is capable of creating excellent articles, then it is trivially true. Probably you mean something else, but what?Well, as to exactly what claim of crowdsourcing I was originally calling false, in this post I cited the articles on Durandus and Roscellinus as evidence against the claim that crowdsourcing makes Wikipedia "instantly responsive to new developments". The fact that these articles are entirely plagiarised or 'copied' from the 1913 Catholic Enyclopedia and Britannica 1911 suggests that Wikipedia is somewhat sluggish on the 'new development' front.
On the other possible claims that William mentions, I disagree that "crowdsourcing makes all wikipedia articles excellent" is trivially false. Since we agree it is false, it follows that crowdsourcing fails to make certain articles excellent, and it is an interesting, and therefore non-trivial, question whether there are certain types of article, or certain types of information that crowdsourcing fails to make excellent, and if so why.
I don't propose to answer these non-trivial questions here - I merely point out that they are obviously non-trivial. I have made suggestions in the past. I suggested that "crowdsourcers are typically shy of deleting material, so articles tend to grow to the point of being unreadable. Second, they have no sense of where material ought to go. So the article tends to lose any basic thread it once had. Third, they have no sense of which facts to include, and which to leave out. What facts about Aristotle would you include in a three page article?". I have also observed that, as a general rules, Wikipedia's coverage of subjects like Boron and set theory is pretty good. On the arts and humanities it is a complete disaster. As Vaknin says, "they are replete with nonsense, plagiarism, falsities, and propaganda".
So it's an interesting question as to whether the poor quality of arts subjects is simply a matter of accident, and could have been the other way round. Another interesting (and therefore non-trivial) question is whether crowdsourcing is better at 'low culture' than 'high culture'. My view is that it is pretty good at articles like this, but really dreadful at articles like this. More later.