The MCU could have just handed the shield to Sam Wilson and made him Captain America offscreen. He could have just popped up in his armor in some MCU debut later down the line, and nobody would have really thought it was weird. However, Feige decided that a story needed to be told about becoming Captain America.
This series could have avoided race. They could have just had Sam fighting the Flag Smashers and left it at that. But it was very important to dissect what it meant to be a Black Captain America. It was the crux of Sam's decision not to take the shield in the first place.
Bucky's acknowledgment that neither he nor Steve could have imagined what it was like for a Black man to wield the shield was a powerful moment. Even Isaiah Bradley's scornful speech about Captain America really resonated. It was essential that the MCU address Sam becoming Cap rather than just thrusting him into the suit because his journey would be much different from, let's say... John Walker's.