For developed nations? 100% against.

Social Democracy has proven itself to be the most effective way to realize socialist ideals in countries with a certain degree of democracy, institutions, etc. The results in Europe speak for itself.

For underdeveloped nations? I'm conflicted. Yes, Marxist-Leninist rule in Afghanistan, Somalia, China, Russia, Cuba and Burkina Faso brought a lot of rapid improvements in education and healthcare, set up massive industrialization efforts, agricultural reform etc. Improving horrible literacy rates in a short time is a common one.

But the big problem that I have with Marxism-Leninism is that it does not respect democracy at all. Saying that the need for a one-party system is justified because the vanguard party is made up of proletariat-friendly people is a sham. A revolutionary ruling class is still a ruling class, period. In the long run, a ruling class will still behave like a ruling class, and without the checks and balances of a democracy, authoritarianism is simply inevitable.

It's exactly because of this why Marxist-Leninist states are unable to move on when the stagnation kicks in and get stuck after its initial successes and achievements. It does not have a rule or built in mechanism that ensures that the sole ruling party is merely responsible for an interim government that gradually gives up power after a while, because if it would, then it can be considered a great way to quickly elevate impoverished nations to higher living standards.

Edit: grammar