Marxist Analysis on The Tale of Two Cities

'It is not the consciousness of men that determines their existence, but their social existence that determines their consciousness.'


To my understanding Karl Marx depicted a life that is thoroughly deterministic, depending upon which social circumstance you are born into, be it a peasant like those a plenty in the streets of London and Paris or a Parisian Marquis, your lifestyle would be fitted around that social class.
Marxism argues for a socio-economic existence of the individual where their social existence is largely determined by the organisation of the state’s economy, they cannot change their social existence through their own efforts much like the peasants of France cannot change their fortunes, for the feudal system affords the Marquess and Monarchy with the state's wealth. Born a peasant, always a peasant. Born an aristocrat, always an aristocrat.
There is a character in The Tale of Two Cities that entirely undermines the key idea being touched here and that is Charles Darnay. Born into the French aristocracy, it was his consciousness that determined his existence and decision to exile himself from his pre-determined social existence and not his aristocracy that determined who he was.
The claim that writers and their stories are 'divorced from socio-economic circumstances' is not true.
It is clear to see that Capitalism is not far from the economic organisation of 18th Century France, where it has turned generations of the French working class into functional objects to allow the aristocracies to profit from their efforts. Built from this socio-economic example of 'working class' and 'poverty' is the alienation of the French peasants to their fury in the revolution against those that hold the chains to their social existence.