•Why it earns a slot
Reread in full, it argues its case with more precision and less slogan than its reputation suggests, before landing on the line everyone actually knows.
Marx and Engels's 1848 pamphlet argues that all history is the history of class struggle, that industrial capitalism has simplified that struggle into bourgeoisie versus proletariat, and that the proletariat's revolutionary victory is inevitable. It lays out concrete transitional measures and closes with an open call to revolution.
This distillation is written from the freely available original, which is always the better read when you have the time: gutenberg.org.