No it's because wealth is unfairly divided.

It shouldn't be, the work isn't evenly divided. People get compensated per mutually agreed upon contracts on the value and contributions of their labor.

Workers should benefit from productivity increase

They do... If you want to argue for stronger worker rights and protections then I'm with you. But to argue that Marxism is some sort alternative is beyond stupid. Marxism is just as bad, if not worse, than Nazism. It's a failed ideology in both theory and practice.

Also, the example in the original comment describes a dystopian death machine.

Humans aren't vegan. There's nothing wrong with meat farms.

A torture factory for cows to facilitate overproduction. We don't need to eat that much meat nor consume that much milk.

Capitalism works on the basis of supply and demand. If there's a demand, there will be production. If there isn't, then the businesses in that industry will either slow protection or close. If that isn't happening then that means there isn't enough accountability in the government.

This is why the entire planet is going to shit...

We're quite literally living in the golden age of humanity. The past 80 years human development has advanced so much in so many places to such a degree that it's an anomaly in human history. The world will always face problems, but humans are very adaptable.