While your comment is from three days ago, I thought its worth answering anyway. Please note that my main goal here is to answer your question, not to argue for or against either their or your position. I also would rather not to explain basics of socialist ideas, so if you have questions that are not that related to the interaction between socialist, specifically marxist, beliefs and cryptocurrencies, I ask you use your preferred search engine instead. For disclosure: my main lemmy account is over on lemmygrad.

Aside from common issues people find with cryptocurrencies, though note that socialists are likely progressives thus issues such as the environmental impact of proof standards may have a higher weight for them, many socialists, including marxists, which that user likely is, looking at the instance choice, may find the reasoning behind cryptocurrencies, to be limited in scope, specifically focusing on how financial resources are managed and who controls aspects of it, while socialists, especially marxists, usually find issue with how finance encourages seeking profit, which, according to socialist/marxist beliefs, is a negative way of organizing the world around us.

In other words, communists don't consider decentralizing finance to be an effective way to take back control over the means of production from the capitalist class, as it does not address the unequal distribution of wealth, which socialists take issue with.