This really gets at the core problems with communism as I see it.

For starters I think the only way for communism to actually work would be with robust checks and balances in place to properly address corruption within the government. AFAIK, basically all communist governments have started as autocracies. That's a really bad combo for corruption. The ideal communist state would arise from democracy, but I don't think democracy will ever create a communist state.

Next, I don't really think state control of all markets is a good idea. A good state would be too slow to react market requirements. You really want your population to self sort and organize as much as possible. That's what makes sure everyone gets all the scarfs they want. That said, I think there are fundamental duties that capitalism does not properly handle. For example, building roads or running a fire department. Capitalism, IMO, works best when there is a truly competitive market in place. Food production would be a good example where capitalism works well (but still might need government support since it's vital to survive).

Now to the USSR specifically (but AFAIK a lot of communist states are like this) the other big problem that goes along with corruption is that there aren't really second chances. I have a coworker that grew up the USSR and he mentioned this with schooling. Fail a class, fall behind, or need extra help and boom. The better job is permanently locked out and you have to settle for a crappy job. A chinese roommate of mine describe a similar phenomena in China. As it turns out, all the wealthy chinese families still ended up in positions of power and relationship ultimately mattered a lot more than competence. I think this mostly comes from the state optimizing for the wrong things. They assume that people wouldn't want to work on farms or that farmers would always want to be farmers. One of the benefits of a capitalist society is that, while no trivial, changing professions is accessible to pretty much everyone.

The core problem with the USSR's version of communism is that it concentrated too much power on too few people (well, and the fact that stalin operated by both being drunk and keeping all the heads of state perpetually drunk). People can get weird ideas (like mao's feelings towards birds) and putting too much power in those individuals' hands is doomed to pain for the citizenry. Some problems are best solved by a little bit of market anarchy.