I roasted MySpace hard back in the day, but now I kind of miss it. I was all too happy to move over to Facebook and leave MySpace behind. For me, the exodus from MySpace to Facebook marks the inflection point were smaller internet communities died and were replaced with services from megacorps. At the time, MySpace was an echo of free homepage sites on providers like AngelFire and Geocities. My friend group had moved…
For me the main thing I miss is Flash. I know there's Ruffle as Flashplayer replacement but the culture around Flash (and most of the authoring tools) has basically died.
(I talked to a bunch of Flash animators I knew back in the day and every single one was surprised to hear that Flash is still available, they just changed the name. Big fail on Adobe's part...)
As for the cute 90s and 2000s web designs, have you seen NeoCities? That spirit is alive and well there :)
The other thing I miss is that everyone would put their email in their form signature and you could just add everyone on MSN. People were super chill in those days, I made a lot of friends that way.
Nowadays the only unsolicited messages I get are from people trying to sell me something.