Yeah but Ashenvale, which was also attacked in the War of Thorns still has Garrosh’s Horde attacking Astranaar over a decade later.
They update it in pockets but the vast majority of the games are time locked to their expansions.
That’s why we have 4 different locations for Dalaran. OG crater in Hillsbrad, Northrend Dalaran, Legion Dalaran and Dalaran ruins in the Isle of Dorn.
Dalaran in the lore as stated by the game is gone, but we can still visit it in different time periods because the vast majority of the game doesn’t get updated with each expansion.