The Threads of Fate system is going away tomorrow. However, you still have plenty of time to make it work on alts, even after Dragonflight Pre-Patch Phase 2 hits!

Based on the official Pre-Patch Phase 2 notes, Threads of Fate will be removed for new characters only and players currently in Threads of Fate can continue through it.

(Source)

Removed the ability for players who have not started Threads of Fate to access the system.

Developers’ note: The goal with Threads of Fate was to help alleviate the linear path of Shadowlands for alts as it was the only way for players to level from 50 to 60. Now that Shadowlands has been moved into Chromie time and Chromie Time’s level cap has been increased to 60, players have a multitude of methods to reach level 60. Players currently in Threads of fate can continue through it, but the option will not be available for any new characters.
We do not have plans to do similar removals with Dragonflight’s Adventure Mode in future expansions. Threads of Fate is a choice to use in Shadowlands and irreversibly changes a player’s character once it is chosen. It previously created two different experiences of Shadowlands, which would double to four with both of the level up and Threads of Fate being accessible within Chromie time. Adventure Mode in Dragonflight  is an overlay to the level up experience and is always on once it is earned regardless of decisions the player makes. 

If you have an alt (or multiple) that you would still like to level through Threads of Fate after November 15, you must start the intro quest before this week’s maintenance. New characters will be automatically forced to level through the Shadowlands campaign if you pick The Realm of Death in Chromie Time.