Resident Evil Requiem's director has explained that returning to Raccoon City was basically to satisfy the developer's own curiosity more than anything.
Resident Evil Requiem is in a unique place as far as the series lore goes. Rather than continue from the aftermath of Resident Evil 7 and 8's Ethan storyline, or return to one of our long-term heroes for one last ride (although Leon is definitely happening), Capcom has opted to bring in a new protagonist while returning to where it all began.
After Raccoon City was bombed off the map following the events of Resident Evil 2 and 3, the series never went back there (outside of prequels and spinoffs). But in an interview with 4Gamer (translated by Automaton), Resident Evil Requiem director Koshi Nakanishi admitted that he always wanted to return to the city, saying the idea of returning and seeing the aftermath is like "rice left forgotten in a rice cooker for a week – something you probably don’t want to open, but eventually curiosity makes you lift the lid."
Nakanishi says that Resident Evil Requiem is both about Raccoon City as much as it is Grace Ashcroft; both have been shaped by traumatic events, with players experiencing the aftermath of her mother's death as well as how the city-destroying incident impacted the survivors of the outbreak all those years later - adding that the "Requiem" namesake refers to how the living remembers the deaths of Grace's mother and the Raccoon City victims.
However, Nakanishi reckons it's still a good starting point for players, as Grace herself doesn't really know much about the Umbrella Corporation or what happened in Raccoon City herself, so she'll be discovering all that alongside the player. But at the same time, I would have to imagine the return to Raccoon City will feature a ton of things you would miss if you weren't familiar.
