The most striking thing for me is that during this period the web felt much more like physical space. I would go to some of these websites just to spend some time immersed in the atmosphere they had so effectively created with this old, pixel by pixel style of design.
The biggest effect of html5/css3/social network era for me is that i no longer give a shit about your website. I might end up on your website if i click a HN link, but the desire to be on your website, with all the sense of place that entails, is completely gone.
And all of these websites are completely gone now too, vanished without a trace. It's like an entire generation of the webs history has been erased.