Let's go to the end of the chapter (and of the quotations):
«The Communists must exert every effort to direct the working-class movement and social development in general along the straightest and shortest road to the victory of Soviet power and the dictatorship of the proletariat on a world-wide scale... World revolution has been powerfully stimulated and accelerated by the horrors, vileness and abominations of the world imperialist war and the hopelessness of the situation created by it, this revolution is developing in width and depth with such rapidity, with such a wonderful wealth of changing forms, with such an edifying refutation of all doctrinairism, that there is every reason to hope for a rapid and complete recovery of the international communist movement from the infantile disorder of 'left-wing' communism.«
In the texts of 1920 «Left-wing» is always in inverted commas.
Lenin, in an outburst of optimism (all revolutionaries have the duty of being an optimist), sees the revolution coming outside Russia, and that's his only concern. When he attributes to it a complex variety of phenomena, he does not certainly mean that, to avoid doctrinairism, we may get rid of the only and unique international features given by the proletarian dictatorship and the destruction of democracy. When he perceived such a danger he did not speak of disorder, but rather of death.
Those who boast of having beaten infantilism in us, have not cured in themselves and in others the left-wing disorder. They died of the right-wing disorder, and they blasphemed Lenin; their corpse shows the violet and repugnant bubo of the opportunist plague.