ICANN moves to retire Soviet-era .SU country domain name

Perhaps, but it's also not particularly bright to rely on the continued existence of a domain whose corresponding political entity hasn't existed since 1991. ccTLD's have an ongoing administrative burden and financial cost to maintain, so it shouldn't come as a surprise that it would go away eventually.

Besides, the signal to start migrating was when they closed registrations of new .su domains in 2022. And the 5-year countdown for removing the domain hasn't formally begun yet (AFAIK), so there's still plenty of time for .su domain owners to migrate away.

Personally, I'm more interested in if/when the British Indian Oceans Territory will dissolve, prompting the retirement of the .io domain.

>But their system administrator actually conducting the change is not, breaking things is against the philosophy of system administration

Knowing when to retire systems and going through the migration and end-of-life period gracefully is an important part of systems administration. We can't hang on to the past forever.