Russia doesn’t have a legitimate gripe.
Russia promised to respect Ukraine’s borders and they violated that promise in 2014.
NATO was nowhere near accepting Ukraine. And Russia doesn’t get to tell Ukraine who they can associate with.
This is about the oil and gas that Ukraine discovered in it’s eastern parts and in Crimea.
But in addition to not wanting a competitor for oil and gas and wanting more of a monopoly status, Russia would also like the grain that Ukraine produces, and advance their desire to regain the territories of the Soviet Union.
The very legitimate gripe they have is violation of Minsk II, the nucleus of the entire issue. They’ve stated this clearly and repeatedly.
Now they are going to enforce it. Anybody that doesn’t like that will have to stop them. The negotiation period is all over.