Besides the fact that it doesnt work because the economic model is broken & real communism can never be achieved and the socialism that procedes it always collapses, there's many theoretical things wrong with communism.
First theres the concept of equality. Is equality actually a good thing? In my opinion, it is not. Inequality breeds hard work, gives people something to look up to, and is how humanity (and nature) has functioned ever since the inception. An ant colony is the pinnacle of inequality. The ant social structure is made out of soldiers, males, workers and the queen. Each are different and unequal.
As such, humans also specialize in things they are good at. And yes, "talent" does exist. Genetics plays a fairly large role in what you are good at& what you are interested in. So does your biological sex.
Communism sees this kind of hierarchy as oppresive and. However, i see it as the natural state of things.
Then the whole concept of utopia is also pretty sketchy... Imagine world peace.. no wars, a one world government where all people are free and everyone should be "happy". But will they actually be happy?
All the great battles have already been won, all the great decisions have already been made.. And now it's just existance, work and weekends to look forward to spend time with family&friends. No future to look upto, no stuggle, no improvements to be made to society, just a mere boring and lethargic existance of mediocrity.
What communist (and liberal) analysis doesn't understand is that humans dont just seek pleasure. Yes, there is a need to satisfy your basic needs drinking, sex, eating and then a whole bunch of needs. But that's not the only thing humans want. Humans also want struggle, self sacrifice. They want to be challenged, they want to make friends and have enemies. Look at how Sup Forums craves for happenings that in reality are tragic events. It's part of a profound human desire to be a part of something meaningful, greater.