If the instance goes down, the network stays up and continues to work, minus only the accounts on mastodon.social. This is not the case on bluesky afaik. They got DDosed a few months ago and the whole network was down because of it. https://news.ycombinator.com/item?id=47802330
In ATProto there aren't 'instances', and its technically 'decentralized' but theres really only bluesky.
I personally think that this actually leads to healthier communities but that may be a matter of taste!
The guy who runs FSE (one of dark fedi's more notable instances) has written a lot of good blog posts on his side of the technical and social details, his one about running FediList is a good picture of the type of one-sided politics involved (and, if you're into the technical stuff, is rich with that too): https://blog.freespeechextremist.com/blog/about-fedilist.htm...