One strength of Marxism is its idealism. It works to expose injustice and fervently believes that all people should be treated with equality and dignity. It asserts that everyone should share abundantly in the wealth of a society. In its vision of a classless world, in which there is no sexism, racism, or ethnic discrimination, it holds up a compelling image of a better life for the exploited. Like Christianity, it too offers hope of a "New Jerusalem": according to Marxism, the inevitable end of history is the throwing off of the yoke of oppression and the creation of a truly just society that will wipe all tears away.
On a more practical level, Marxism offers good ideas for alleviating economic inequality, such as lowering interest rates to almost zero to spur economic development and taking out the drag of other "rents" in the economy that produce nothing and yet suck out money that could be employed for useful purposes.
It rightly questions whether it is better to build a highway that can carry goods to a distant location or erect a garish palace as the monument to one person's ego. It argues for the social benefits of free education, free health care and state run utilities—benefits that can be adopted even by an economic system that does not want to come near to embracing Marxism.
On the negative side, however, a major weakness of Marxism is that it leads to state tyranny. When the state owns everything, it can easily repress individual freedoms, behave arrogantly, and badly misallocate resources. Classic Marxism sees this period of state ownership as a temporary experience that will end with the withering of the state in favor of a utopic anarchy, but it offers no realistic path for achieving this goal.