Capitalism is a system that will always result in long-term oppression of the workers and consumers, corruption of governing bodies, and environmental destruction.

This is because the base idea is wrong. Adam Smith and the Capitalist theorists that came after him claimed that the invisible hand of the market would trend towards better outcomes for the workers and consumers. This would be true if the best way to be profitable was to do good, but that isn't the case.

More often than not, it is more profitable to do harm than good. Firms that seek to always increase profits, which is the fundamental goal of a Capitalist system, will always be incentivized to get as many people as possible to pay as much as possible for as little as possible.

This has been demonstrated over and over again. Think about software platforms for the most recent example. Netflix has only gotten more expensive with worse content and harsher usage rules. Same with YouTube, Twitter, Reddit, Facebook, etc. This is called "enshitification." Companies always want to make more money, that can only happen by charging more, giving less, or creating some kind of production efficiency. And what's the quickest way to make production more economically efficient? Fire workers and make the remaining/replacement ones work harder for longer with the same or worse pay.

Those are some of the practical reasons Capitalism is bad. The theoretical reasons have to do with the way Capitalism tries to justify private ownership and the employee/employer relationship.

How is it ethical that a man who has never set foot on a factory floor, never operated a machine, never worked a double shift because he needed to feed his family, to reap a majority of the produced value of that factory simply because he owns it?

How is it ethical that a man simply because of his privilege of upbringing, can "earn" 100-200-300X more than his average workers? Does he produce 300X more value? Does he work 300X as hard? Is his position 300X more difficult to perform? No, it's because Capitalism justifies such grievous disparities and in fact, rewards them.

Answer this: The person who is told, "you are free to either be abused, or to die." Is that person free in any significant sense?

I used to be a Capitalist, hardcore one actually. But slowly I came to realize that it can only result in one thing long term, collapse and dystopia. I'd be happy to discuss this stuff further with you, just DM me, maybe we can chat more on Discord or something.