The Soviet Union’s issues were very complicated.
You do have a point that, at least economically speaking, Communism was an improvement over the Tsarist near-feudalism that came before. However, one could argue that any economic system would’ve been an improvement over that. Still, even Marx thought that Russia was a bad test case for Communism because its assumptions were based on an industrial society and Russia at the time was pre-industrial.
Kasparov argued that one thing that led to the fall of Communism in the Soviet Union was the fact that an economy controlled by planning everything from the top cannot be dynamic and innovative over the long term. You need the ability for random people to come up with the next big thing in order to have a truly dynamic and innovative economy. Of course, he’s not an economist, so you need to take what he said with a large grain of salt, but he does raise some interesting points with examples of technical innovations made in the capitalist world due to people willing to take risks with the hope of “making it big.”
One problem is that modern Capitalism seems to have more in common with Soviet Communism than it does with “classical” Capitalism. Instead of government bureaucrats charting the course of the economy, you instead have oligarchs/plutocrats who run large corporations running the show. As a result, it’s harder to achieve said dynamism because those in power want to try to maintain the status quo and keep milking whatever profits/capital they have and therefore make it harder for the random little guy to upset things with an amazing new idea. Add in difficulty in getting the education necessary to be able to create highly technical new inventions due to high cost, the fact that one quitting their job to start the next big enterprise may be highly risky as a single illness can result in bankruptcy or death, and various other problems and we have a lot of the issues we see today. I forget the article or the person who stated it, but a while back I read an article by a younger, successful entrepreneur who, despite being very successful in this current climate, is worried that it’s about to collapse in on itself due to being, as he put it “crony capitalism” instead of “true capitalism.” He argued in favor of living wages, higher taxation on the wealthy to finance the ability for the less well off to have a chance to make it, and so on, less the wealthy will be dealing with masses of people armed with pitchforks and torches outside their homes.
Communism probably would work best in a post-scarcity society, and even Marx claimed that a post-scarcity society would be Communism’s eventual end goal. For example, many people argued that the Federation in Star Trek is essentially Communist. It works there, though, because Federation citizens have lost interest in personal profit and it is effectively a post-scarcity economy. So long as enough people are interested in personal gain and are able to acquire power to achieve that goal, I don’t think any “pure” human economic system would work. That’s why I advocate for more hybrid economic systems, but that’s based less on proper academic analysis and my own views looking at history of current and recent economic systems.