@jerry The endgame is likely that we start seeing Fediverse servers spin up with an allow-list that auto-ignores / auto-blocks all other servers until and unless an admin explicitly admits them.
We saw a similar pattern with email when the spam problem began to tilt towards intractable (in that while you can spin up your own email server, good luck getting Google or Microsoft's servers to accept and transmit your messages if you have no history at all).
(What's that Gibson quote? "It started with an inverted killfile...")