According to the developer, Starfield Creations released through Bethesda's Verified Creators program will no longer block achievements in the game. Creations are mods made official through the developer, and mods have always been an important part of Bethesda's games. Starfield is no different, as the developers have released their own paid mods alongside free ones in the Starfield Creations store.
The official implementation of achievements in Starfield Creations was announced in the November update, as described on the official Bethesda website. The update also includes quality-of-life improvements and new content for the game.
"If you already have a Starfield creation installed, we encourage you to keep an eye on the Creations menu in Starfield or Bethesda Creations page for its achievement friendly status. Achievements will not retroactively unlock on previous game saves with Creations, even if those Creations are now achievement friendly."
Players have long requested this feature and now can use Creations throughout the game without blocking achievements. However, the developer noted that only certain Creations have the option to be achievement-friendly. Players will have to keep an eye out on the creation store for which mods are achievement-friendly.
Mods Are Important To Starfield's Identity
Console Players Can Enjoy Achievements and Mods
Achievements on Xbox are important to many players, and this update allows them to attain them when using mods that Bethesda makes available. Starfield Creations can range from singular missions to a new vehicle, like the Deimog land vehicle available in the November update, but can also drastically change the game. Starfield's "Leave No Witnesses" mod, for example, eliminates the 30-second timer players have to deal with witnesses to their crimes, giving players more leeway if they want to pursue a pirate's life in Starfield.

Latest Starfield Patch Adds A New Buggy And Plenty Of Performance Fixes
Starfield's latest patch celebrates the game's milestone of 15 million players, giving everyone access to a new land vehicle and fixing several bugs.
The Starfield community has also been receptive to the new update, with some speculating that more modders will put their mods on the Creations page now that they potentially won't block achievements for others. According to Reddit overhaul how NPCs work and gain a new experience from Starfield.
Our Take: A Step In The Right Direction
Making Mods Easier To Get Is Better For Everyone
Bethesda already embraces mods to the point that the studio releases official mods for Starfield, and only making their official mods achievement-friendly has been detrimental to Starfield players. Community mods can make a game more fun or address issues even the developer misses. These Creations have been a core part of Bethesda games like Skyrim and Fallout, and Starfield integrating them for a wider audience signals a step in the right direction for Bethesda. Hopefully, Bethesda's next massive RPG won't wait so long to make mods and Creations achievement-friendly from launch.
Sources: Bethesda, Tramonoto83/Reddit