In the transition to SC2, many of Brood War's iconic units would be transferred over to a new engine and a new game. However, in the case of the carrier, some subtle details ended up getting lost in translation in the transfer process.
In the infographic above, I've outlined three of what I consider were the most important factors for the carrier's usefulness in intense micro situations. These factors combined in important ways to create a synergy effect which allowed skilled players to consistently fire at targets from maximum range (leash range).
There were other differences in addition to those outlined (such as interceptors below a certain hp/shield threshold in BW automatically returning to the carrier to regenerate), but in my view these additional differences don't impact basic control as much as the listed mechanics.
All of these mechanics have already been covered by Nony in his 2012 video comparing BW and SC2 carrier mechanics.
Blizzard did patch the carrier in Heart of the Swarm, presumably in response to that video. Though, they ended up adding only one of the functionalities Nony covered in his video. What Blizzard's carrier patch fixed, was that it allowed a player to retarget between living targets in leash range.
I'll link Nony's video here as well for those who prefer to have it explained in a different medium:
Ahli's BW Carrier Mod
The point of this article is not to repeat all of this information, but rather to inform and create awareness around an existing and fully functional, fully data driven implementation of all these mechanics. The modder Ahli (teamliquid profile, reddit profile) is behind this mod, and it's based on an earlier trigger based solution by decemberscalm (both were involved in helping out starbow).
Ahli is also involved in other Blizzard games, helping out in the Heroes of the Storm community with his Observer UI. I'd pay extra attention to this guy's feedback in the future Blizz!
The mod is called: BW Carrier Micro Mod 1.6.
Amazing attention to detail. No triggers.
Retargeting returning interceptors
Trailing Interceptors and immediate deployment