The internet has come so far and changed so much in my lifetime, but I also grieve almost every day for what we've lost along that journey.
Decentralized networks used to be the default, from IRC to Usenet. When they were centralized, adversarial interop allowed things like Trillian and Pidgin to flourish. So much more used to be client-side, so that you owned your data in a meaningful way. Perhaps most importantly, it used to be much easier to put your stuff on the web.