In all three instances, a smaller country has declared its alignment to a certain ideology and wishes to become closer to superpowers with said ideology.

I think you basically said this, but: The revolutions in Cuba and Vietnam were primarily focused on national liberation. Their Marxist ideology and affinity with the USSR was secondary to their actual, material liberation.

The recent history in Ukraine is essentially different in that the current government is largely a creation of external (mainly US) influences. It’s really hard to frame the push for Ukrainian NATO membership as a democratic ideological stance in the same way as the nationalist anti-imperialism of Cuba and Vietnam.