Not only did Cryptic remove a bunch of zones with Jewel of the North, but there are other ways in which it feels like the game has oddly regressed.
For example the Ebon Downs storyline is back to concluding with the Throne of Idris dungeon - an instance that was in the game at launch, got removed with Elemental Evil, and then just became accessible again occasionally during the Tales of Old event. It feels pretty retro to just get sent back in there at the end of the zone for a quest... with the main difference that it can now be soloed.
Also, I remember I used to think it was pretty neat how Tyranny of Dragons expanded various levelling zones, added dragon heroics to them, and introduced players to the concept of progressing a campaign while levelling. This first half of the campaign has now been removed, and the zones that remain and that used to have dragon encounters in them have been shrunk back to their previous size.
This is such a strange module.