TL;DR: Crowdsourced content systems can have only 2 of the 3: Authorartive, Comprehensive, Upto date. Systems like Wikipedia and Stackoverflow miss either one or more of these characteristics. The article claims to have found the "solution" to this problem which is simply having experts for high level areas who invite experts for sub-areas to create the content.
I don't know why authors think this is different or novel or scale to something akin to Wikipedia or Stackoverflow. In a way, the article doesn't even look honest as it cherry picks examples on SEP that look great and examples on Wikipedia that look bad to justify its grand claims.
The article overall is biased towards authority of some elite "experts"
over more democratic, collaborative, community-driven work.
Sketching SEP as the only hero that saves internet from being an
information junk while calling rest of the internet as, "thrash leap" is
just grandiose. The Internet is full of examples that show "quality"
content is possible. And why is the obsession over "quality" content?
The internet is not supposed to be only restricted to use of
"information retrieval".
In the article, Wikipedians are called, "non-experts", while there are
many experts in their field who also contribute to Wikipedia. Speaking
of which, why not suggest those "elite" authoritative authors to
contribute to Wikipedia?
It is also claimed that, "The internet should look more like the SEP."
What? The internet is basically an extension to our capabilities of
communication. And how we use it reflects our communication habits.
Saying "the internet should be more like SEP" is like saying everyone
should communicate informative encyclopedia entries to each other in
their daily lives. Variety of other uses of internet, and thus
communication, is ignored. The article fails to recognize the value of
"piles of opinion, speculation, and misinformation", which eventually
make up the "quality" content that it advocates. In fact, as human
beings, we are supposed to have all that "speculation", "opinion", and
more importantly, "fun".
While I unhesitatingly concede that the article is biased in favour of expert editors, I think you slightly miss the point with the following remark:
> In the article, Wikipedians are called, "non-experts", while there are many experts in their field who also contribute to Wikipedia. Speaking of which, why not suggest those "elite" authoritative authors to contribute to Wikipedia?
The problem is not that experts don't contribute to Wikipedia. The problem is that you usually don't know whether or not an expert wrote whatever you are currently reading. What makes SEP different to Wikipedia is that you know exactly who wrote the article (it even gives you the author's email address) and that you know for sure that that person is an expert in his/her field. That is a guarantee that you simply do not have with Wikipedia and many other Internet knowledge resources. This is not to say that all information on Wikipedia is bad, it simply says that you can't have a guarantee.
This, of course, is not only Wikipedia's greatest flaw, it is also its greatest strength. The Wikipedia model sacrifices authoritativeness in favour of being up to date and comprehensive (in the sense of covering all subjects). And that is a valid trade-off for a site that wants to be a knowledge base for the whole world.
The SEP will never reach the size of Wikipedia, but then again, that is not its goal. Its aim is to be an authoritative source for academics in the field of philosophy. Within this well-defined field, it aims to be comprehensive and up to date. It caters to the needs of scholars, who need something (or rather somebody, a physical, known author) that they can actually cite in their own work. Wikipedia can never give that, and neither should it, for then it would no longer be Wikipedia.
Lastly: although I completely understand your criticism of the all-encompassing claim that "the Internet should look more like the SEP", I'm sure most people would agree that it wouldn't hurt to have a few more places around that you know you can trust for serious information. And incidentally, that is just what the author is arguing, if you hadn't taken his subheading out of context ;-)
I don't know why authors think this is different or novel or scale to something akin to Wikipedia or Stackoverflow. In a way, the article doesn't even look honest as it cherry picks examples on SEP that look great and examples on Wikipedia that look bad to justify its grand claims.