[cesarb]

> For comparison, the internet mostly transitioned off of TLS 1.0 just fine, why can't we do the same for transitioning off ipv4?

This is a great demonstration of the advantages of the end-to-end principle. The reason the transition off TLS 1.0 (and earlier SSL 3.0) could happen so quickly is that only the endpoints (the server and the client) needed to be updated to understand the new protocol; nodes in the middle of the path (routers, switches, and so on) only needed to care about the IPv4 (or IPv6) layer, which didn't change with new TLS versions.

But that only works for layers above the network protocol; when updating the network protocol itself, every node is affected.

(And the TLS transition also took longer than it should, in large part because a lot of "middleboxes" violated the end-to-end principle by inspecting or even modifying the TLS connection, without taking part in the protocol negotiation. TLS 1.3 had to be modified to pretend to be a resumed TLS 1.2 connection to trick these middleboxes into not incorrectly rejecting the newer version of the protocol.)