Please do elaborate.
However, his predictions are only a part of a very rich body of work that still provides productive economic analysis.
That said, I also don't believe in it. From what I'm seeing around me, people usually grab small short term advantages over other people even if they suffer long term consequences together after the "success". Also people really love to give power over themselves to other people. Until these two misconceptions are overcome there can't be any real attempt at communism.
I would argue this is a symptom of capitalism, not an inherent property of human nature. We live in a system that requires us to compete to sell our labour in order to survive. This leads us to think of everything in terms of competition.
This is why so many people in creative jobs (including software development) end up feeling like they can't do their work efficiently because their manager won't let them. Because the employer-employee relationship is based on exchange, it is fundamentally antagonistic.
Science, technology, engineering, and mathematics all makes money as a multiplier for the capitalist class. So all of them are highly praised. However, those pesky things like philosophy and art are "worthless" - as in they don't make the owners money.
Marx's works also talk about turning universities into training centers too. Eventually, the cost of education would be the point that either the rich (capitalists) would attend, or regular people would attend to learn how to work in the above (STEM) categories.
This one is well known and profusely commented, I'm sure you can google it: Marx considered industrial workers the ones with more class awareness and predicted that Socialism will ignite in the UK first.
On the contrary, it succeeded in big old agrarian countries like Russia and China.
Also predicted that worker class solidarity will make for an idilic proletary dictatorship, no need for democratic checks and balances that only decadent burgeois countries need.
Then came Lenin, Stalin, Mao...