Russia, France, Germany, and Ukraine held Normandy peace talks back in January, some of the things the Russians asked for (paraphrased): Russian-speaking regions of Donetsk and Luhansk would be granted special status within Ukraine, security guarantees from NATO, a limitation of the number of troops stationed in Eastern Ukraine, and Ukraine restoring the fresh water supply that they cut off from Crimea. Conceding on some of those things might have been a good alternative to war.
Ukraine is a democracy. It's not up to us or anyone else to "ensure their neutrality" if that's not what they want. We already refused to allow them into NATO under the guise of "ensuring their neutrality" and look how that turned out.
It's a country similarly corrupt as Russia (oligarch wise), that's used as a puppet to pressure it. They have big foreign involvement, and even had their democratically elected leader toppled just 8 years ago. Nominal democracy and huge foreign influence are not contradictory, rather they are the norm.
Doing the opposite of how you ensure their non-neutrality as another country.
Don't use them as pawns against Russia, don't get them into NATO, and have Russia sign and respect that - and ensure their borders from Russia and everybody else, fighting for them if necessary (not merely with hypocritical sanctions and condemnations after you've sacrificed them).
