I think their point in mentioning it is understanding the barbarity of the capitalist world order.

The question of "how [socialism] could work out" can be debated endlessly, but the grave element of the question is how to prevent liberal capitalism from being restored and how to survive capitalist encirclement. The libertarian navel-gazing about "incentive to work" and so on has always been bullshit and is frankly not a real issue.