Shadowlands took 2 years, Dragonflight took 3.
Given that only a small force of Azeroth was inside the Shadowlands, let’s compare what little this time gap has done to the lore.
I’m going to use the example of the timelapse between Warcraft 3 and Vanilla WoW, which took 4 years.
In those 4 years:
Orgrimmar was built
Teldrassil was grown
Blood Elves reclaim some parts of Silvermoon city
Taurens settle inside Mulgore and build Thunder Bluff
Stormwind is finished with the construction
The undead have transformed the undercity into their capital.
Let’s see what happened in the timegap of SL and Dragonflight:
Lor’Themar and Thalyssra got married.