Yeah, democratic socialism has never worked. I'd suggest Engel's On Authority as a primer for why authority will always be needed.
As for the theoretical basis for using authority, we can look to Marx, Lenin, and Stalin:
""Between capitalist and communist society lies the period of the revolutionary transformation of the one into the other. Corresponding to this is also a political transition period in which the state can be nothing but the revolutionary dictatorship of the proletariat."
-Marx
"You will have to go through fifteen, twenty, fifty years of civil wars and international conflicts, not only to change existing conditions, but also to change yourselves and to make yourselves capable of wielding political power." - Marx frequently critiqued programs on their unwillingness to take up arms or use organized proletarian power to protect socialism. It has been the downfall of several socialist efforts, even including the USSR which fell to counter-revolution in '91 (the seeds of which crept in long ago and could hav been dealt with).
"The dictatorship of the proletariat arises not on the basis of the bourgeois order, but in the process of the breaking up of this order, after the overthrow of the bourgeoisie, in the process of the expropriation of the landlords and capitalists, in the process of the socialisation of the principal instruments and means of production, in the process of violent proletarian revolution. The dictatorship of the proletariat is a revolutionary power based on the use of force against the bourgeoisie." - Stalin in Foundations of Lenninism
"The dictatorship of the proletariat, i.e., the organization of the vanguard of the oppressed as the ruling class for the purpose of suppressing the oppressors, cannot result merely in an expansion of democracy. Simultaneously with an immense expansion of democracy, which for the first time becomes democracy for the poor, democracy for the people, and not democracy for the money-bags, the dictatorship of the proletariat imposes a series of restrictions on the freedom of the oppressors, the exploiters, the capitalists." - Lenin in State and Rev
I'd ask you now to turn your attention to the liberal 'democracy', or democracy of capital over labor. In the US for example, we have a one party dictatorship of capital, where both ruling parties cater to slightly different interests, but nonetheless uphold and expand the capitalist project at home and abroad.
Recent study on US as an oligarchy: https://scholar.princeton.edu/sites/default/files/mgilens/files/gilens_and_page_2014_-testing_theories_of_american_politics.doc.pdf
Resources on USSR democracy:
Resources on USSR 'repression' (always need to ask, who was being oppressed?):
Resources on China:
https://github.com/dessalines/essays/blob/master/socialism_faq.md#is-china-a-democracy
