> I am not sorry, this does not impress me.

I don't think it was meant to impress. On the contrary I think the overarching point of the whole article was that it's okay to not know things outside of your domain that may seem trivial to other CS folks.

> Not knowing modern CSS - how can this person possibly work in any sort of cutting edge web development and not know about that?

Well, I don't know how he does it anymore than you do. But it looks like he's still working on cutting edge web development and it seems to be working out, so my takeaway is that he doesn't need to know about it plain and simple.