Did Marx unwitting condemn us to capitalism without end? As noted in the linked post. The idea that capitalism should continue until its potential had played out was a disastrous mistake. The potential of capitalism is infinite and will continue with a millennium of slaves, as things become progressively worse. Th point rather is that a broad phase of general development can initiate a transition to postcapitalism, and this had better be underway at all phases of the developments since the end of the eighteenth century.
The whole of the current left in most of its forms is too shallow to be useful, or effect anything, while the doctrinaire theorists of Marx are too constricted by theory to open the window for some fresh air.