If by "well maintained" you mean keeping a whitelist of instances, then yeah. But I doubt anyone is doing that because it's actually counterproductive to the concept of fediverse. By keeping a whitelist you are creating an in group and an out group and instances can live or die based on that grouping.
As for why you'd need a whitelist, you can't defend against a malicious attack if they keep spinning up new instances with bots designed to spread misinformation. The moment you ban once instance another one gets spun up. The only solution is a whitelist so all new instances are automatically blocked. Of course that works if all "normal" instances also have proper registration policies and can't become attack vectors.
If the fediverse becomes wildly popular defending the instance can become a full-time job as the open nature gives more attack vectors. Also most instances are ran by volunteers so it's probably not going to be a good time for anyone.
I'm pretty sure some of them are objectively broken. I had a mission where the mission givers partner was seeing someone else and I had to figure out who. The process of figuring out who the person was was pretty cool. Outside of some vague physical traits my leading clue was the mystery persons partners job position. I had to look up every restaurant, break into every single restaurant, find all the people who worked that position, find where they live, break into their apartments to find who their partner was and if they match who I'm looking for.
Eventually I was 99% sure I got the right person, but I needed proof they were seeing each other. I combed their entire apartment, found nothing. I combed the partners apartment, found nothing. I checked their workplaces, found nothing. I tailed both of them the entire day, still found nothing. I even checked their mailboxes and found nothing. I literally ran out of ideas how to solve the case because I found nothing.
Turned me away from the game because I got this cool investigation with some really out the box thinking, and then didn't get rewarded because I didn't find that last piece of information.