It was quite far away, for a multitude of reasons. There are many different factors, but this is a very broad summary of why the Soviet Union was never “real” communism.

First off, the communism Marx intended for was mainly for advanced industrialized western European countries such as England, France, Germany. This is because the more advanced and industrialized the country, the more distinct class distinction was, with more worker manipulation taking place by the owners of the means of production. This is because with industrialization, the need for a lot of workers decreases, so there was more and more competition for the jobs remaining. This leads to worsening conditions and wages because the workers fighting for jobs left are willing to work for cheaper and longer because they’ll do anything really just to have a job. Marx thought that as this progressed, the workers, or the proletariat, could reach a class consciousness of what was going on and could take the means of production from the bourgeoisie (ruling class) in a revolution. Marx thought that the conditions of the workers in relation to the owners would be so bad that they would reach class consciousness inevitably, and all it would take is for someone like Marx himself to point out the worker manipulation taking place.

What Marx envisioned happening was that once the workers took the means of production, there would be a TEMPORARY socialist government which helped the transition to a communist society. Engels created the term “withering of the state”, which was Marx’s idea of socialism in which the temporary socialist government would slowly wither away as the workers would eventually be able to self govern without the need for a state, which would lead to a communist society. Essentially, a communist society would have 0 government or state, with the people collectively owning the means of production to produce the needs of the society. Each person would contribute what they can in terms of work and skills, but ultimately be free to hunt, fish, write, partake in the arts, as they please, without anyone in particular owning any private property, because private property is what leads to state formation, capitalistic society, manipulation of workers, etc. To get rid of private property, there has to be means of production available where any need by the people such as food and shelter can be met collectively.

But, eastern Europe and its regimes were nowhere close to being an advanced industrialized society, and class divisions were nowhere nearly as prominent. The means of production were quite weak due to the lack of industrialization. Most of the USSR (Tsarist Russia before) was essentially peasants, with a very small ruling class, but not to the degree as western Europe. So, Lenin, inspired by Marx, decided that an elite revolutionary class must bring revolution to the region despite the lack of industrialization, along with class consciousness not being reached by the working class, because the working class itself was not as clear as it was in more advanced countries. His justification for speeding up the process and bringing revolution to a place in Marx’s eyes not ready was because he believed there was no time to wait for industrialization, and that basically it would take too long. Many argue his primary motivation was mainly egotistical, and his opportunistic attitude altered what Marx was after. So, when the bolsheviks took over and the previous Tsar left, the ideally socialist transitionary government took power, but because of unclear class divisions, there was a lot of different groups aiming for power. Along with that, World war 1 was going on at the time with Russia fighting both other countries and internal fighting between the previous regime and the many different factions within Tsarist Russia, such as the Bolsheviks, which essentially destroyed the countries economy. When the Bolshevicks and Lenin took power, the country was in such shambles that it was very evident they weren’t even close to being able to self govern because of the lack of means of production of food, etc. Once Lenin died, Stalin took over the party, and the civil unrest of starvation and poor living conditions led to both the strengthening of Stalin’s regime, along with the millions of deaths as a result of the totalitarianism and need to maintain power.

So, to sum up your question, the brutal dictatorship that arose in the Soviet Union was completely different then Marx’s communism because in Marx’s vision a communist society had no government. The socialism described by Marx and Engles was meant to be very temporary and help ease the transition post revolution to a self governing society, but in the soviet union that transition phase never withered away and the political party in power stayed in power. Essentially, the USSR never reached communism, and no country ever has reached communism. Every country gets stuck when opportunistic people or political parties take power post revolution and never leave. Yet, many modern day marxists say that because the Soviet Union, or any “communist” country was not and hasn’t yet reached the “end stage” capitalism, had very little clear cut class divisions, and essentially no wide spread working population had real class consciousness about their manipulation by the ruling class, that it may still be possible for a communist society to form. They claim that as capitalism continues to advance in today’s society, with the wealth gap between the owners of the means of production and the working class continuing to rise, wages continually lowering, and competition within the working class rising to the tipping point that a revolution of the working class will be inevitable, as Marx predicted. But, a counter argument to modern day Marxism would be that capitalism always seems to find a way to adapt, and things like union formation, universal basic income, are all adaptations to keep workers from reaching any form of unified class consciousness. A good argument regarding modern day marxism could be whether or not this adaptation has an end point. And of course, one can easily play the human nature card if they wanted to, as a strong argument can be made that humans may very well be incapable of such an endeavor even in proper conditions, because we simply are too dangerous to self govern. Many argue power to be extremely easily corrupt-able, so any attempt at communism will fall short due to the difficulty of the transition state ever actually withering away as Marx and Engels had idealized.