Ukraine is an independent sovereign nation _de facto_ and _de jure_, recognized by probably every single country in the world including the aggressor russia to.
Why you thing I have "a dog in this race"? It's just old-school war, russia does not know how to use it's soft diplomatic power. It's threats all the time, and when Ukraine does not give up on idea to westernise for at least 8 years - russia treat is a threat - thus they invade.
If I'd compare - I'd compare it to Winter War. When WW2 started - they saw that Finland is too close to St.Peterbug for russias comfort - thus they started the war. Same here - Ukraine wants to free themselves from post-soviet economy and modernise to western model, it's a threat to putin - because then the "western" economical and political borders will be too close for his comfort.