Ukraine was an independent country that was moving towards closer ties with the EU and had an agreement ready to sign. Putin interfered, put pressure on the incumbent president who then unilaterally decided not to sign. Yes there was protests in the street but it was the elected parliament...
Exactly what else do you think he EU should do? If not sanctions, which weren't imposed on Hitler, the alternative would be to send force into Ukraine!
I certainly agree that it was the most significant point but did they draw back because of the lessons learnt previously and knowing that at that time they did possess the power to destroy the world.
'Perceived appeasement'? Are you saying that wasn't Chamberlin's policy towards Hitler prior to the war, whether or not he had an alternative at the time?