My core issue with Facebook, Twitter, Instagram, VKontakte, and other commercial, centralized social network services is that they all eventually drift away from "staying updated on your friends' lives" towards "getting world news", "communicating with businesses", "a town square", "a place to look at ads", "endless supply of brainrot", and all kinds of other things that involve the platform forcefully shoving strangers at you and you at them - I call such pivoted services social "media". If you want to just be with your friends on the modern internet, you're out of luck. (Yes, messaging apps are a stopgap seemingly everyone has settled on, but it's not a good solution.)
This gaping niche is what eventually got me interested in developing for the fediverse and why I started Smithereen in late 2019. My goal with this project is to eventually bring back that long-forgotten "early Facebook" experience when the platform just gets out of the way and lets you have fun with your friends and meet new people in groups. And to do it such that no one will take it away this time.
There are profiles with lots of fields, walls, groups and events public and private, photo albums with tagging, and more.
One important feature that's absent for now is global user search and, somewhat related to that, a database of educational institutions so you could put your school/college/university on your profile and be findable by your classmates. This is just something that's very hard to do in a decentralized system without partially centralizing it, although I have a few ideas that need experimental validation.
It's written in Java, it only has a few external dependencies (imgproxy, MySQL, and a web server of your choice), and it ignores most of the so-called "progress" that happened in web development over the last decade. The UI is a meticulous reproduction of VKontakte's pre-2016-redesign layout. It's fully compatible with Mastodon and other ActivityPub servers in the sense that its functionality is a superset of Mastodon's. Its client API is mostly compatible with VK's as well. A server for a few users should be able to comfortably run on a Raspberry Pi or a cheap VDS.
Unlike most fediverse projects, there is no "flagship" open-signups server because I have more interesting things to do with my life than running one of these; it's a serious commitment that fits neither my goals nor my personality. That said, I set up https://try.smithereen.software so anyone could try the thing with a temporary account (you don't need a real email either).
Looking forward to your feedback!