think you don't really understand the difference between communism/socialism and the USSR/CCP. The definition of communism is somewhat vague, as it can be interpreted in multiple ways, but generally it goes along the lines of: a political system with common ownership of the means of production, in which there are no currency (or money of any kind) and classes. As you can see by this definition, neither the USSR nor the CCP fall into those categories, as both have had the classes divided.
Economy needs a solid and measurable intermediary unit of trade, which is currency backed trade replaced barter system which was flawed in and clumsy in everyday practice, cashless or in case of Marxist/socialist/communist labour based economy, types of labor, quality and amount of labor still has to be measured by something and using subjective and inheritely unequal concept as basis for anything is impractical. Cashless society is impossible unless you want to return to monkey
Your criticism of Marx is somewhat valid, though it doesn't really have a lot to do with the ideology itself.
I mentioned before how Marxism defies human nature, contradicts itself at multiple points and is a philosophical thought experiment, a flawed man creates flawed ideology that is hip with the unthinking knuckledraggers who follow cults of personality, a tale old as time.
My response to your point about competitiveness: overall correct, but competition isn't sustainable in a capitalist market. This is observable in large companies like Google and Apple who have pretty much ended most of their competition with very few exceptions. This is because of the way the free market allows for larger companies to stomp over smaller ones, and this has been observed through history many times before, so it isn't a recent phenomenon.
Life is unfair, much like in business, large companies cemented their place in the market economy and provide service in highly competitive market, smaller companies are bought by bigger companies and are incentived to innovate, make wise decision that drive profit and innovation. Companies like Google and Apple form bipoly market for a reason, both innovate, a dopt and develop new products, learn from their mistakes and are beholden by Investors to make profit as much is it possible. Current bipoly competes for talent and will buy out small companies if they deem that to be wise. Free market is unpredictable and there isn't such thing as "too big to fail” See sinking Disney, fall of IBM, Atari and many others. Like in nature weak should fear the strong and bigger party has every right take out the smaller party, adapt or become irrelevant in big picture.
Communist economies are planned economies and are bidden by the state produce exact same products and services, often driven by state subsidies like in CCP and late USSR. Competition is surface level at best and darling company of the week get special treatment, see Lada, ByteDance and Huawei for often propaganda purposes. All of these companies in closed off economies are controlled by the state. The little guy has as much room to compete if they do not produce something utterly groundbreaking, which is rare. Closed off economies are isolated and are forced to work on older technology, rely on copying and IP theft (see CCP shenanigans)
My response to your point about state-mandated employment: you are, again, somewhat correct, but only if we focus on the examples provided by non-communist countries. Also, companies aren't voluntarily giving you protections. If there was no government regulation, most companies would attempt to fuck you over in every way possible
Communist countries banned unions, prevent ability to strike, write contracts which both parties are obligated follow by law, the state sets up everything, including wages that defy reason with guarantee of fair working hours we end up with poverty level monthly wages, below 800 USD per month in rubles, yuan, etc. This barely covers cost leased apartment, heating, water and electricity. Cost of food and healthcare are barely covered after this.
There's a reason why USSR built commie block ghettos for imported serf class to live in, mass overproduction to give illusion of higher GDP through which to give illusion of efficiency and prosperity to casual onlooker. These by the bulk two to three room apartment often lacked running water, proper building standards. Not to mention non-existent healthcare or ability to save for crises. Since you worked to eat, live and live in a pod of are part and parcel of majority of communist life.
Unlike in socialist/communist system in free market economies minimum wages are, set employer-employee contracts guarantee living wages, protection for your services that you bring to the company, leading to competition for your work experience and level of training. More valuable you are as worker, more leverage you get for benefits. Not to forget since workers unions are banned in socialist/communist countries you aren't given opportunity to get fair third party representation that negotiate terms, safety nets, workplace safety, fair work hour compared to wages. Lastly as for healthcare, since in communist and socialist system private healthcare and insurance companies do not exist. Everything is run by and owned by the state. In event of something life altering like a stroke, debilitating diseases and costly auto-immune diseases aren't covered by private insurance companies that do not exist in communist/socialist countries.
Moreover due to lack of lack of social safety nets, private pension firms communist/socialist system can cut anything and everything at whim. Like I mentioned before you're likely to live hand to mouth in a collective owned ghetto where you won't own anything and be happy little bugman in modern day kolhoz.