I get what some users mean when they criticize projects in this manner. They're saying, "You're so smart and this is all you came up with?" It's not so much an insult as it is disappointment of a talented person. Their mentality is "If I had your talent, I wouldn't have wasted my time on this."
But it's important to understand that the whole purpose of side projects is to take a journey, learn, experience, and try out random things. It's impossible to tell accurately weather a project succeeds or not so you have to try.
I'm sure if Sergey Brin and Larry Page submitted their Google prototype on HN it would have been met with "Why? There's already Yahoo, AOL, Microsoft, Lycos, Alta Vista... they do search and they're established, Page Rank is just a feature. What's stopping Lycos or Alta Vista from implimenting their own Page Rank algorithm?". Twitter would have been met with "Only 140 characters? That's not going to get anywhere". (all things that a VC would say)
I blame this on Hacker News (emphasis on HACKER) having more startup news than projects, inventions, designs, code samples, and hacking articles. The emphasis on success starts to drown out the emphasis on coding for fun even if you fail. Oddly enough in the Mixergy.com interview with Paul Graham. At exactly 49:40 Paul says, "[hacker news] was originally called startup news but after 6 months we changed it to hacker news cause we got sick of reading about nothing but startup stuff."