This hypothetical is unproductive in my eyes cause it's too reductive and possibly misleading about the importance of Democratic centralism. For it to be of any use you would have to flesh out a connection between the cause of the failure with the Democratic centralism, and the horizontal approach too actually, so this is a quite a pointless exercise otherwise, it is more honest and productive to ask if you have to organize a resistance and anarchy and Democratic centralism weren't options how would you organize said resistance. But then again I fail to see the benefit of this exercise in speculation, specially given how hard it is to speculate about it.
By the nature of your question I imagine you might have some concerns about Democratic centralism, bring them up debate them let's go straight to the issueshe.