Warsaw pact was a socialist fortress in a capitalist world. It is more properly seen as proto-socialist, the same way the maritime merchant republics in medieval Europe (like Venice) were proto-capitalist. Have Leninists become wiser from the failures of the Warsaw Pact? Depends on the "Leninists" in question since many different kinds of people adopt that label.
I am less interested in that question than I am in the question of setbacks in general. You might not like Deng, but Deng said the following:
https://www.marxists.org/reference/archive/deng-xiaoping/1992/179.htm
>I am convinced that more and more people will come to believe in Marxism, because it is a science. Using historical materialism, it has uncovered the laws governing the development of human society. Feudal society replaced slave society, capitalism supplanted feudalism, and, after a long time, socialism will necessarily supersede capitalism. This is an irreversible general trend of historical development, but the road has many twists and turns. Over the several centuries that it took for capitalism to replace feudalism, how many times were monarchies restored! So, in a sense, temporary restorations are usual and can hardly be avoided. Some countries have suffered major setbacks, and socialism appears to have been weakened. But the people have been tempered by the setbacks and have drawn lessons from them, and that will make socialism develop in a healthier direction. So don’t panic, don’t think that Marxism has disappeared, that it’s not useful any more and that it has been defeated. Nothing of the sort!