Your arguments rely on the sole premise that socialism was either not achieved or failed in the Soviet Union and China. But the historical facts prove otherwise.

1. The Bolsheviks succeeded in their revolution and managed to establish a socialist state. The “collapse” of the USSR seventy years later is irrelevant and does not change this fact.

2. Marxism-Leninism is realistic and not idealistic. It prioritizes the consolidation of the revolution and building socialism at home before getting drawn into volatile revolutions abroad.

3. The soviet workers did have democratic control over their production. Not as individuals, but as a collective. This control was exerted through so-called Primary Party Organizations present in factories, farming collectives and neighbourhoods. Similarly, China has enterprise party branches which are crucial for management.

4. China has shown the opposite of backpedaling into private enterprise. Since the start of this century, the state has been stricter in regulating non-public enterprises and directing them towards the social goals that are set up by the five year plans.

All of these points can be fact checked and there is plenty of academic research done on them. I can recommend for starters Roland Boer’s works.

What happens when your revolution successfully topples the government, the corporations, how do you coordinate production and distribution?

Just like other socialist states have done in the past and presently: you let the workers control and manage the existing factories, farms and enterprises according to what they seem fit; you organize them and provide them with enough training and education. There are plenty of lessons from history in that regards which one can learn from. I don’t know why you seem to think this to be a difficult matter.

Well, history until now has favored revolutions over electoral campaigns. Should the socialists get elected into power, what would guarantee that the reactionaries do not interfere and overthrow you? (I have Chile’s Allende in mind here, or Jan 6th). It doesn’t matter how socialists get to power really, be it through elections or revolution, the point is that it is imperative and inevitable that they need to consolidate their power or else no socialist project can outlast them.

The USSR achieved quite a lot, but I don’t think they achieved socialism period

Socialism is by definition a transitional period between capitalism and communism, so in that sense they did achieve it. The whole point is to gradually transition into communism without disrupting citizens’ livelihood.

Sure, but such reform must come after the revolutionary party overthrows the ruling class and cements its rule. The Soviet Union, for example, did not achieve socialism overnight (see the New Economic Policy), however the Bolsheviks had to consolidate their power first and foremost against the reactionary and counterrevolutionary forces. The goal is to impose reforms ourselves, and not beg and demand it from the bourgeoise, or else such reform cannot be guaranteed. If you agree with this stance, then you may be a Marxist-Leninist.

The weapon of criticism cannot, of course, replace criticism of the weapon, material force must be overthrown by material force; but theory also becomes a material force as soon as it has gripped the masses. Theory is capable of gripping the masses as soon as it demonstrates ad hominem, and it demonstrates ad hominem as soon as it becomes radical. To be radical is to grasp the root of the matter. But, for man, the root is man himself.

Marx, Critique of Hegel’s Philosophy of Right.

Democratic socialism implies that socialism is not inherently democratic. The whole ideology sprouted from Western leftist critique of existing socialist systems in countries like the Soviet Union because of their supposed authoritarianism. Marxists-Leninists rather speak of “socialist democracy” which is “the rule by and expresses the will of the rural and urban workers, who comprise the vast majority that had been exploited by and excluded from the benefits of capitalist democracy.” (See Boer, Socialism in Power, Chapter 4). How this is achieved is through the "dictatorship of the proletariat” which makes of the workers the masters of their own country. The employment of the term “dictatorship” may seem antithetical to democracy at first glance, but the reality is that the dictatorship of the proletariat aims to suppress the former ruling class while simultaneously ensuring mass participation in democracy for the formerly suppressed classes. In practice, this has been ensured through both participatory and consultative democratic systems in local and national levels, while preserving the leadership of the communist party to avoid the resurgence of counter-revolutionary outbursts. This is the case in all existing socialist countries, such as the PRC, Cuba, Vietnam and so forth.

The merits of Democratic Socialism on the other hand can be assessed by asking one simple question: has it historically ever succeeded in establishing a socialist state? No. That is because democratic socialist parties on the ground have been more concerned with creating guardrails for capitalism rather than progressing the revolution. While reform is always appreciated, the reality stays the same: as long as there is capitalism, the working class will remain exploited, and no amount of reform can fix this crucial component. Revolution, despite its violence, remains the only path forward towards socialism because of the inherent contradiction between the interests of the working class and those of the ruling class who’s unwilling to give up the benefits it gets from oppression domestically and abroad.