SNAP might be a terrible investment at this point (I tend to think so because I don't think they can overcome challenge from Facebook) but based only on your points above, we'd have to conclude Google is "worthless" as well no?

Selling something vs nothing is a good metric to think about, but "advertising" is certainly not nothing. In fact, it's a multi-billion $ industry. It just so happens to be dominated by Google and FB currently, who are both "fundamentally" selling something real.