I understand why people think this chapter filler-like if you are not enthusiastic about culture. However, I believe Chapter 1048 is much more meaningful to Japanese readers, because it actually elaborates the cultural & historical importance of Japan Fire Festival by using the perspective of Wano background.
People pray for bumper harvest, peace and health in Fire Festival. The flashback was kind of explaining why the festival existed in first place.
Japanese suffered a lot from wars, natural disasters and droughts in their history. In some fire festivals, snakes symbolize the bad things, and people use fire to exterminate them. That’s why Kaido and Orochi were burning in this chapter (snakes and dragons are the same thing in some Japanese mythology).
One Piece stands out a lot among all the manga in Japan, and even the government is promoting it. Good storytelling is actually not enough to achieve this status, since there are lots of manga with excellent storytelling and everyone has their own preference. And this chapter is the reason, because One Piece explains the ideals of Japanese very well, so of course they consider it as a representation to their country.