Disney is removing "Slave 1" from Star Wars as the name will no longer be associated with Boba Fett's iconic ship.
While Disney and Lucasfilm have yet to officially comment, LEGO designers Jens Kronvold Frederiksen and Michael Lee Stockwell confirmed that Disney doesn't want the term used anymore while questioned by the Jedi News fan site who noticed packaging doesn't mention the name:
Jens: Then, the next one, also from The Mandalorian, is Boba Fett’s Starship.
Michael: Yes, I built another. We’re not calling it Slave I any more. This is Boba Fett’s Starship.
James: OK, why are we dropping the Slave I name?
Jens: Everybody is. It’s probably not something which has been announced publicly but it is just something that Disney doesn’t want to use any more.
While the specific reason wasn't stated, obviously Disney doesn't want their Star Wars characters or Boba Fett associated with "slave."
Boba Fett is a bad guy
I don't believe the reason why Boba's Fett ship was named "Slave 1" has ever been made known, but the ship first belonged to Boba's father, Jango Fett, and obviously implies something dark and sinister as the pair are bounty hunters who capture and imprison people. To be clear, they are not good guys, but maybe since the new Boba Fett Disney Plus series might feature the character as an anti-hero, Disney doesn't want to call his ship "Slave" and will instead refer to it as Boba Fett's Starship per above.
Wiki describes Boba's Fett Slave 1 in part as the following where we see mention of "more secure (and less humane) prisoner cabinets":
According to in-universe reference material, Slave I is a modified Firespray-class patrol craft produced by Kuat Systems Engineering. Unique in design, the Firespray-class has a distinct engine cluster on which the ship rests when landed, but when in flight the ship rotates 90 degrees so that the top-mounted cockpit faces forward. The ship's artificial gravity similarly reorients depending on the flight mode, while the rotating stabilizer fins on either side carry repulsorlifts to assist with landing. The class only saw limited production, as it was considered too heavily armed for civilian use, too underpowered for Kuat's home fleet, and too reliable for post-sale maintenance business. Jango Fett chose the vessel for, among other reasons, its anonymous appearance, but heavily modified it with additional weaponry, expanded crew quarters and more secure (and less humane) prisoner cabinets.
After inheriting Slave I from his father, Boba Fett made additional modifications to the vessel. These include a secret (and stolen) military sensor-jamming and masking device that enables the ship to disappear from most sensor systems, immobilizing bunks for up to six prisoners, and even more weaponry. Armaments include 2 Borstel GN-40 twin rotating blaster cannons, 2 Dymek HM-8 concussion missile launchers, a Brugiss C/In ion cannon, a Phylon F1 tractor beam projector, and 2 Arakyd AA/SL proton torpedo launchers.
Again, I always thought of Boba Fett as a bad guy and part of the Empire, but maybe not anymore? What's next?