For me personally, I’m not necessarily anti-capitalist as a whole; I think it has its place. I think people incorrectly place how old capitalism actually is. Sure in the Medieval Period, people bought and sold goods like how we think of markets, and they even had currency to exchange for it, but it was still much more of a bartering based system. Capitalism itself is also a very cultural phenomenon, only emerging out of Europe (in India for example, capitalist thinking was anathema to the cultural norms and took many years to take hold once the British invaded). In reality, there was a period of time in which all of a sudden, resources in Western Europe and the Americas become suddenly abundant and a system had to be put in place to handle that, and the system was capitalism. Here’s some of the main problems, some of which have been pointed out by others:

1. Capitalism is based off of a system which inherently assumes infinite growth which is not possible

2. Free markets require easy and free access to information to govern things like price setting, but that information is almost impossible to obtain accurately

3. Capitalism even in its purest form is not a complete enough theory for governing an entire economy. Capitalism only has mechanisms for providing resources (money) to workers and capitalists (owners) which leaves out a full third of the population. That last third are non-workers, primarily made up of the old, the disabled, children, students, home caregivers, and temporarily unemployed

4. Capitalism enforces power imbalances in a population that make capitalism less effective. For a market to work most effectively, all parties involved (buyers and sellers) should be on equal footing, but they never are and never can be

5. Less of a functionality point, but I personally believe that there are some things that morally shouldn’t be governed by a market structure such as healthcare or food access

As parting thoughts, I would say that capitalism is not a bad thing in the short term. It’s effective at getting a country going to the point where they can become socialistic in the future. Karl Marx himself based his theories in “The Communist Manifesto” and “Das Kapital” on Adam Smith’s “The Wealth of Nations”. He also said that “capitalism is pregnant with socialism”. Capitalism is a tool to get to an end goal, it isn’t the end all be all system it’s made out to be though, and it’s also not the only tool that can get you there (see the economic theory of developmentalism).

Sorry for the long post, but I thought the detail was necessary.

TL;DR: Not a bad thing in and of itself, but a flawed system it’s time to move on from