The strategy of Last and First Men is to create a superset of marxism-in-history (i.e. the developmental history of…) in order to broaden the context of discourse for a ‘left communism’ (LC).
One of the traps of the strain of historical materialism is to pit that ‘ism’ against all other philosophical perspectives, as a gesture that transcends all of them. That’s both totally unlikely and completely confusing even to those who agree with marxist fundamentals: it is confusing because it beggars the sense of different viewpoints.
It is important to study the history of the emergence of the initial marxist perspective to see its historical context, and isolation.
Last and First Men creates, not an ‘ism’, but a ‘theatre of dialectic’, where ‘dialectic’ means a field of parallel philosophies.
A good example is the Axial Age as context that is larger than the spiritual/material dimension.