What unites the philosophy of Kant, Fichte, Schelling, Hegel, Feuerbach?

All of the above philosophers-representatives of the school of German classical philosophy of the 18th-first half of the 19th century .. it largely predetermined the development of European thought for decades to come: the entire philosophical discourse of the 19th century was built around their ideas.
It was with the German school that the development of the idea of the supremacy of the idea of man began: God faded into the background, great attention was paid to the reliance on experience-empiricism. In fact, their ideas were given a start by the Great French Revolution with its motto about freedom, i.e. the primacy of man over God, the state, etc.