However, the pages are still active via /review/first-posts and /review/helper respectively - presumably to allow users to see their stats on them (my links point to Stack Overflow's review pages, but the behaviour is the same on all* Stack Exchange sites).
On the pages, instead of a notice saying that the queues have been retired, there is a confusing message:
Instead of having the message says that I need 2147.5m reputation, perhaps the message should say, e.g.
This review queue has been retired.
or something similar - in addition to having the "Retired" indicator next to the review queue's name.
* Based on a sample size of 3 sites: Stack Overflow, Meta Stack Exchange, and Super User.