Marx observed proletarian division but did not revise his theory

Evidence

Neither Marx nor Engels were unaware of the proletariat’s failure to become a universal class. Both studied the Irish Question closely, were active in the attempt to resolve its destructive impact on the historical processes of English working-class formation, and commented on its import for future proletarian organization. Nevertheless, the impact of their experience with the English proletariat on their theory of the proletariat’s historical role appears to have been slight. — Cedric J. Robinson, Black Marxism_ The Making of the Black…, 268