Samsung ONE UI is for flagship phone, i mean for higest processor. Where UI can be optimized well with processor. But lowest processor, i mean midrange phones can be given ONE UI but it can't be optimized well with this processor. It is not possible to do as much as you want. So these problems happen, but they try to fix at least as much as possible through new updates according to the budget. And if the problem is not fixed, then there is nothing to do, you can go to the flagship.