There are plenty of regions in Europe that have similar histories and few countries in Europe are really that old, even states with long histories have not had constitutional orders lasting more than 50 years. Finland was a part of Sweden for 600 years, Denmark part of Norway for an equal amount time. Neither of those facts in any way reduces the Finnish or Norwegian people's right to self determination.

Waging aggressive war is a violation of international law - The state of Ukraine is the legitimate successor to Ukrainian SFR and if Russia has any claims on its territory those must be pursued through legal means.

There is nothing complicated about the Ukrainian question, it is simply a part of Putin's strategy of death by a thousand cuts. Last time that strategy was used Europe was thrown into a conflict that made the world say never again to nationalism. The Russian people would have done well to listen to their grandfathers now that this conflict is all but forgot.