I'm glad it shocks you.
Self determination is what powerful countries/forces grant to less powerful groups when it serves their purpose, or the powerful have no claim to it, or when empires fall apart, or when the group agree to subservience, or is in the middle of nowhere, or where they call home has nothing powerful countries want, or isn't already taken by a group with powerful friends.
Go Google the list of groups agitating for self determination worldwide, it's a very, very, very long list, where are we for them?
I'm replying out of courtesy, posts with....
"megalomaniac in Moscow"
Or
"Self interest for us is not having a country that will do literally anything to destabilise us"
Are simply not serious.
To quote the great German Chancellor Otto Von Bismark...
the Balkans were “not worth the bones of a single Pomeranian grenadier”
Yet the Balkans dragged us in to the First World War.
What is happening in Ukraine is terrible, but it's not our war, it's not worth a single British OAP dying of hypothermia.