Marx analysed how the capitalist approach lead to alienation, dehumanisation and exploitation.
In order for capitalism to work, goods must be produced - humans are therefore not at the centre and so are alienated.
A worker must produce the goods for a higher class person. The lower class, called the proletariat become the workers and they are simply a part of the big production machine.
Working in a factory the worker is unable to show at all a creative side. They are alienated from the product as well as the upper class.
When the proletariat receives their wages it ultimately gets returned to the benefit of the bourgeoisie through rent and shops.
The proletariat must rise up against the bourgeoisie
If humans understand the situation they are in then the idea of historical materialism will teach them that they must change their situation by action.
For Marx the people should strive for a communist society. A society achieved by action not ideas.
Marx believed that religion made people unaware of their own suffering. He believed it to be a tool used to control the people.
On a theoretical level Marx's approach is a far more person-centred way to run society. It is right to centralise the idea of removing oppression.
Marx is also successful because it provides a clear analysis of society. It helps people to reflect on the basis for how their society is run and aims to abolish the class system.
Capitalism does not necessarily involve exploitation and Marx has a narrow view of what society is like. There are plenty of harmonious societies that operate under capitalism.
Where Marxist thought has been implemented it has often collapsed. The communist states of Eastern Europe are a key example of this.
Even in societies that run a communist state, there remains injustice.