I think what's being said here is that it's easy to pick up the ideas of visual design, not the actual skill (I hope). As a budding designer, Dribbble is definitely helpful in allowing you to see "the bar" and improve how you approach certain projects. However, it is most definitely NOT easy to "pick up [visual design] by cruising Dribbble."
Design is a solution to a problem. It doesn't matter what the medium is. Sometimes you see these solutions on Dribbble but more often than not what you see are examples of style. They are two separate things.
Your definition of design includes style, since style can (and often is) a solution to a problem as well. Not everything is wireframes and usability, and this is coming from someone who's first book on the job was Jakob Nielsen's.
Ever read Blink? Or those studies about how people make an unconscious decision about a website in less than a second?
Style and polish expresses a level of quality (at the very least) and can also communicate the type of site. Is this a kid-friendly Disney site? Is it a serious financial tool? Is it a mysterious stealth mode startup?
I'll concede as much. I was drawn by the fact that the discussion was about design, and you two went off into style land. It'd be about the same as us starting a talk on Rock and Roll and we really just dive into guitar solos while swearing it's rock we are on about. Make sense?