"First, it has been reproached as an invitation to people to dwell in quietism of despair. For if every way to a solution is barred, one would have to regard any action in this world as entirely inefective, and one would arrive finally at a contemplative philosophy. Moreover, since contemplation is a luxury, this would be only another bourgeois philosophy. This is, especially, the reproach made by the Communists"

-- Sartre, second paragraph of Existentialism is a Humanism, https://www.marxists.org/reference/archive/sartre/works/exis...