You might as well discard the entire Marxist movement as "utopian garbage". Here is what Marx and Engels wrote in the communist manfiesto:
"The Communists are distinguished from the other working-class parties by this only: 1. In the national struggles of the proletarians of the different countries, they point out and bring to the front the common interests of the entire proletariat, independently of all nationality. 2. In the various stages of development which the struggle of the working class against the bourgeoisie has to pass through, they always and everywhere represent the interests of the movement as a whole."
As to why the working class is important, Marx and Engels wrote:
"Of all the classes that stand face to face with the bourgeoisie today, the proletariat alone is a really revolutionary class. The other classes decay and finally disappear in the face of Modern Industry; the proletariat is its special and essential product.
The lower middle class, the small manufacturer, the shopkeeper, the artisan, the peasant, all these fight against the bourgeoisie, to save from extinction their existence as fractions of the middle class. They are therefore not revolutionary, but conservative. Nay more, they are reactionary, for they try to roll back the wheel of history. If by chance, they are revolutionary, they are only so in view of their impending transfer into the proletariat; they thus defend not their present, but their future interests, they desert their own standpoint to place themselves at that of the proletariat.
The “dangerous class”, [lumpenproletariat] the social scum, that passively rotting mass thrown off by the lowest layers of the old society, may, here and there, be swept into the movement by a proletarian revolution; its conditions of life, however, prepare it far more for the part of a bribed tool of reactionary intrigue.
In the condition of the proletariat, those of old society at large are already virtually swamped. The proletarian is without property; his relation to his wife and children has no longer anything in common with the bourgeois family relations; modern industry labour, modern subjection to capital, the same in England as in France, in America as in Germany, has stripped him of every trace of national character. Law, morality, religion, are to him so many bourgeois prejudices, behind which lurk in ambush just as many bourgeois interests."
Here is a section of Trotsky's Permanent revolution.
"A democratic dictatorship of the prolelariat and peasantry, as a regime that is distinguished from the dictatorship of the proletariat by its class content, might be realized only in a case where an independent revolutionary party could be constituted, expressing the interests of the peasants and in general of petty bourgeois democracy – a party capable of conquering power with this or that degree of aid from the proletariat, and of determining its revolutionary programme. As all modern history attests – especially the Russian experience of the last twenty-five years – an insurmountable obstacle on the road to the creation of a peasants’ party is the petty-bourgeoisie’s lack of economic and political independence and its deep internal differentiation. By reason of this the upper sections of the petty-bourgeoisie (of the peasantry) go along with the big bourgeoisie in all decisive cases, especially in war and in revolution; the lower sections go along with the proletariat; the intermediate section being thus compelled to choose between the two extreme poles. Between Kerenskyism and the Bolshevik power, between the Kuomintang and the dictatorship of the proletariat, there is not and cannot be any intermediate stage, that is, no democratic dictatorship of the workers and peasants.
The conquest of power by the proletariat does not complete the revolution, but only opens it. Socialist construction is conceivable only on the foundation of the class struggle, on a national and international scale. This struggle, under the conditions of an overwhelming predominance of capitalist relationships on the world arena, must inevitably lead to explosions, that is, internally to civil wars and externally to revolutionary wars. Therein lies the permanent character of the socialist revolution as such, regardless of whether it is a backward country that is involved, which only yesterday accomplished its democratic revolution, or an old capitalist country which already has behind it a long epoch of democracy and parliamentarism."