what was old internet in 2007? netscape navigator and usenet? was their an 'old internet' aesthetic associated with that
It definitely isn't as strong a nostalgia as it is today, ofc. Today we're talking about aesthetics and culture nearly 2 decades old, but I frankly don't remember a lot of people wishing to go back that much back in 2007 (That would be '87! Most people wouldn't even have connections to any nets at home!). Definitely a lot of "back in my days" about mid-to-late-'90s though. As far as I remember, the digital "aesthetic" culture wasn't as strong as today, so people didn't really associate any particular aesthetic with the old net, though this might just be my then-disinterest speaking.
Also please keep in mind forums existed all the way back to the '80s,
Delphi Forums is 42 years old! Feels like you think the "old internet" is newer than it is, the beast that was IRC was declining heavily in 2007, in fact I believe it lost majority of its users by the early 2010s, if not late 2000s. MySpace was about to see its peak user counts in a year from then, and and then very quickly get overtaken by Facebook within the same year or the next. GeoCities was on its tail-end, and would be shutdown in 2 years in 2009. From 2005 to 2010 is the transitional era from the internet that was, to how we know it today. What I remember is pretty much wide adoption of social media, with some minimal resistance. Forums continued strong for a while though, I remember the forums I was active on still being active in early-but not mid-2010s. 4chan was a new thing back then, in fact it was the first imageboard that I've used, and the first one I know to be really popular outside Japan. It was like, 3-4 years old by that point.
So yeah, what would people be nostalgic about on the net in 2007? Depending on how old the person is it's either going to be usenet, BBSs etc. (though I always felt like those people are the most excited about the new stuff too, I'm a bit too young to be nostalgic for those, neat stuff though) or literally the same things people are nostalgic about today like forums, geocities, IRC etc.