I agree with the slant of your argument. A very narrow definition of self-determination that means “our country” can be unhelpful, even worse calamitous. Case in point, South Sudan and Somalia.
If my ethnic group, the Mada people were to secede from Nigeria, I can guarantee the government of “Madaland” won’t be any better than what is obtainable in Nigeria.
We need to be more imaginative as a people and be more sensitive to people and their idiosyncrasies.