Exactly appeasement led to the second world war.
Countries stood back and let it happen.
The USA did not even join in till they were attacked half way through.
Russia will continue attacking countries until they are stopped.
Their invasion of Ukraine is just testing the water, none of the countries on their borders are safe from attack.
I don't think this situation is comparable to the Second World War. There was no alliance like NATO back then, and whatever alliances or agreements might have existed were for the sake of temporary convenience, mainly between countries acting in their own selfish interests, not as part of an international coalition. The League of Nations had no real power, just as the UN is impotent now.
However, NATO is not impotent, and Russia knows full well that if they attack any NATO country, they'll be facing the full force of the entire alliance, of which three members are nuclear armed. So, even if Russia does attack a NATO country, we really don't have much to worry about. NATO will demolish them.