I'm concerned that people are already eager to bury the fediverse and unwilling to consider what would be lost. The solutions I keep hearing in this space all seem to hinge on making the place less equal, more of a broadcast medium, and less accessible to unconnected individuals and small groups.
How does an instance get into one of these archipelagos if they use allowlists?
Same thing with reply policies. I can see the reason why people want them, but a major advantage on the fedi is the sense that there is little difference between posters. I think a lot of this would just recreate structures of power and influence, just without doing so formally--after all the nature of scale-free networks is large inequality.