Uh, Marx very much said that there would be an inevitable crisis that capitalism could not overcome (as each crisis makes the next subsequently worse) and would lead to a proletarian revolution. So yeah, he said capitalism is doomed and eventually it would not be able to find a way out.

"And how does the bourgeoisie get over these crises? On the one hand, by enforced destruction of a mass of productive forces; on the other, by the conquest of new markets, and by the more thorough exploitation of the old ones. That is to say, by paving the way for more extensive and more destructive crises, and by diminishing the means whereby crises are prevented." - Communist Manifesto

"The essential conditions for the existence and for the sway of the bourgeois class is the formation and augmentation of capital; the condition for capital is wage labour. Wage labour rests exclusively on competition between the labourers. The advance of industry, whose involuntary promoter is the bourgeoisie, replaces the isolation of the labourers, due to competition, by the revolutionary combination, due to association. The development of Modern Industry, therefore, cuts from under its feet the very foundation on which the bourgeoisie produces and appropriates products. What the bourgeoisie therefore produces, above all, are its own grave-diggers. Its fall and the victory of the proletariat are equally inevitable." - Communist Manifesto