ITZY is not flopping they are successful both int'l and in Korea. Yes they're not losing popularity in Korea the reason why their song doesn't chart that high is because their song is not the taste of Koreans (lol sorry for my English) and I think JYP doesn't care about that because their goals are in the international charts.
But what do you think is the domestic charts really a big deal and they need to focus about that? Or just continue their goal to int'l success because it's not a big deal