The MCU would look very different if Ant-Man didn't return from the Quantum Realm in Avengers: Endgame. After Thanos decimated half of all life in the universe at the end of Avengers: Infinity War, all hope seemed lost for Earth's Mightiest Heroes, with many of their own ranks being turned to dust following Thanos' snap. Avengers: Endgame picked up five years later, showing how difficult the members of the Avengers had found it to move on from their unprecedented defeat, though a glimmer of hope was provided when Scott Lang, a.k.a. Ant-Man, returned from the Quantum Realm.
https://screenrant.com/ant-man-avengers-endgame-no-return-effect/