Since there's so little pro-capitalism sentiment on the fediverse (or maybe it's just lemmy, in either case I couldn't find much) I'd like to start posting some arguments for capitalism. I'm not an expert, so I don't know that what I'm saying matches what a capitalist who knows what he's talking about might say. Let me know if I'm way off please.
One of the basic ideas behind capitalism is competition. There are multiple companies competing for your money. It is of vital importance for each of them that they collect more consumer dollars than they spend. This ensures that they are making a profit and can keep growing their business.
To ensure that one company gets your business over another, the company will produce the highest quality product for the lowest price. They'll desperately explore how best to make a particular product, what products consumers want, the best ways to deliver that product to the consumer, and the lowest price they can sell that item for while staying in business. They are doing everything in their power to make dealing with them more pleasant for the consumer than dealing with their competitor would be. That's how they compete.
This means that you get an efficiently made product, that you wanted, in an easy to purchase place, for a low cost. What's more, this incentive didn't come from regulation (which will be ignored or exploited as much as possible) or altruism (which is unreliable and exploitable), it came from a self-interest. Capitalism takes the most selfish, ambitious, and talented people, and it forces them to stay up at night thinking about how to best please others.
Similar mechanisms protect workers. Companies compete to buy your labor. This makes it in their interest to pay you well (up to the value you can provide the company), provide good working conditions, and give you deals that have many perks and bonuses in your favor. If they didn't do that, another company could buy your labor instead, forcing your previous employer to either offer you a better deal, or search for a substitution. The issue with the latter though, is that substitute would also take better paying jobs (or jobs with better work conditions) if they were available. So long as there is competition for workers, companies will be forced to provide quality work environments to ensure that they can hire and hold onto someone.
When there's no competition, there's no incentive to provide quality goods or services. You can charge high prices, you can have inefficient development, you can make bad products, and there's no consequence. In fact, you might not have any incentive to make anything at all, preferring to simply be given money. The end result is nothing of any value is made on large scales and people are oppressed and controlled without any form of control over their oppressors. That's what socialism is. Removing competition removes any material incentive to please the people.