For system changes...

Graphics update
New raid planner in the game
Beast master
Viper
Pictomancer
Two dye slots
Save dye favorites
Specs as actual gear slots instead of fashion accessories
Ability to make blacklisted players disappear or filter terms
Fantasia can be re-used for 60 minutes of logged in /playtime
Can do ventures via the companion app
Cosmic Exploration is technically new, although should be similar ish to the Firmament
Deep dungeon will function a bit different somehow
Option to hide players around quests
Messages display in the middle of your screen for mechanics
Emotes/recipes display next to quests when they need to be pressed
Climb up ladders

This wasn't announced anywhere, but a casual observation I personally noticed in the media tour: bicolor gemstone drops are 16, get buffed by Forlorn Maidens to 20, and by having the Twist of Fate buff (24). Combined with the announced cap increase to 1,500.

Probably other QoL they will leave for the patch notes.

They said there are more announcements to come after 7.0.

But obviously this game has had a formula since the start and they mostly stick to it. It's the same stuff as usual. So you either like what they produce each expansion or you don't, but at least you know what to expect.