Some risk will be necessary. At some level we do have to let small instances with minuscule communities exist and participate in the wider fediverse, otherwise this whole thing will just fiat centralize.

The cautionary tale is email. In a way, Email is the most successful decentralized protocol. Anyone can technically throw up a client and start communicating with any other email server. The problem of course, is that if you do this in practice, your email will almost never get through to the majority of people. Why? Most of the large providers of email have formed what amounts to a whitelist of trust, and either outright reject participants they don't recognize, or subject those outside participants to incredibly high standards that they themselves to not have to abide by.

So, email has practically become a centralized affair controlled by a few big stakeholders. A lot of small email providers have gotten out of the game in the last decade because they're tired of dealing with it. It's a mess.

I'm not against greater tools, but I'd inject that health is not solely measured by the lack of spam. A spam-free fediverse that's just one instance and its three closest friends is not healthy. Whatever solutions are developed should leave open the door for small instances to still participate and have a honest chance at survival.