An alternate version of Thanos destroying Captain America's shield is revealed thanks to newly-emerged concept art for the successful Time Heist mission, every single one who perished from the snap five years prior came back - including their allies, which gave them the boost needed against Thanos and his minions. However, prior to their return, the task to take down the Mad Titan was only on Iron Man, Thor and Captain America.
The MCU's main three heroes were kept separately for the most part of Infinity War, so seeing them teaming up was a treat for fans. However, it wasn't an easy fight, with Thanos relatively easily beating each one of them. At one point, the Mad Titan was even able to destroy Captain America's shield - slashing half of it using his battle axe. The scene, apparently, could've gone a different way as revealed in a new concept illustration for Endgame.
Marvel Studios Head of Visual Development Ryan Meinerding shares his illustration on how Captain America's shield could've been destroyed by Thanos. Instead of the Mad Titan breaking it to half, the villain would've punched directly through it, shattering the shield from the center. Check out the Endgame concept art below shared on his official Instagram .
This moment would've looked cool on the big screen, especially for Thanos, since he wouldn't have needed his battle axe to destroy the typically indestructible vibranium shield. It would've effectively reinforce just how strong he is even without the help of the Infinity Stones, and that would've come at a good time considering that much of Endgame leading to that was focused on the heroes. However, this scene would've robbed Captain America a subtle moment that sums up everything one has to know about him. In the movie, after his shield was cut in half and was down on the ground, he didn't think of giving up. Instead, he tightened the straps of his broken shield, signaling that he had every intention of continuing the fight despite the odds of him winning it. Fortunately, back up came right in time to help him, Iron Man and Thor take on Thanos.
Steve Rogers may no longer be in the MCU, but with external factors making things difficult for him to carry out the responsibility bestowed upon him by Steve.
Source: Ryan Meinerding