Capitalism was built on slavery by the British and other Europeans which entailed owning humans and treating them as animals, as your property and doing what you wanted to them, be that murder,torture,rape,child abuse, neglect. How many people were taken as slaves and used by the early capitalists? one million died and 10-28 million were kidnapped to be used as animals. The capitalists accumulated vast riches from this racist slavery working children to death and giving no rights whatsoever to these tortured tens of millions. During this time first the Lords then the capitalists stole the land from the smallholders in the UK driving them into homelessness,begging and starving.
The capitalists and their various states would then use their imperialism to oversee massive and repeated mass starvations all over the world from India to Brazil by stealing the food these countries kept for times of crop failure.

These starvations and robbery as well as instigating wars would destroy India , China and many other countries for hundreds of years. Although the history of fuedal Europe is one of war this would be taken to new levels by the capitalist empires in the 20th century although the Tiaping and Boxer rebellions in China agianst the imperialist occupiers and the ruling class would also see 20 million killed mostly by famine.

Then we have two capitalist world wars and 100 million dead.

The advances from capitalism are immense in every field.It is a stage of development of the productive forces that fits in with the move from fuedalism-merchantilism to capitalism and industrialisation and after all of the above horrors on a scale that the world had never ever witnessed before or since we have a dominant empire for 70 odd years which has maintained the misery and suffering around the world by maintaining imperialism in order to keep it with far more than all the rest. The US imperialism started more hidden than the previous capitalist empires of Europe but could not maintain that for long and now it has what 300 military bases around the world? and is above ALL international law.

Development of technology has undoubtedly increased from the accumulation of wealth by capitalists but with it we have a violent unstable empire that does what it wants and demands full spectrum dominance and a war every 2 years, we have a capitalist ruling class that own all the means of production so have 100% power since the end of the Soviet peace camp (Other than China , Cuba etc). We have 10 or so people owning the same wealth as 3.5 billion people,a US empire that is a failed state as is the UK with debts racked up to 20 trillion,we have a planet that has been destroyed by capitalism and who knows where that is going to end and we have all the ensuing trauma of all of that.

We could move on to the next stage in human development called socialism but i fear we are not advanced enough spirtitually being mired in the small I and materialism. Of course we had many inventions from socialism that were given to us in capitalist states that involved taking people with nothing and giving them everything they could want from full literacy and free education to full training and full employment, living in slums to living in good houses and no existential fears of homelessness or unemployment and destitution that are a corner stone of capitalism. Socialism brought us womens equality and the vote before capitalist countries did and an economy that lived within its means with practically no debt and products made to last not just be thrown away but easily fixed. Free health care for all was first started in the Weimar republic but only realized properly in the USSR and socialist countries. Socialism has given us so much from worker control of factories and economic growth that never dipped with all of the benefits above and everyone working with each other as a collective and not fighting for everything. Working for peace and an and to all wars.
 

Capitalist sympathisers will usually regurgitate the same arguments when discussing socialism. For instance they will often say stuff along the lines of:
The unfortunate reality is when you give people a large amount of stuff they don’t all get the same.

The only people saying that everyone should get the same are people that don’t know anything about socialism as in socialist run countries people get paid all sorts of different wage levels, its just that some don’t get insane amounts to the detriment of everyone else, as you do in capitalism.

Where did socialism fail? Most people in Russia wish it was still there as do most in former DDR,Romania and many others in fact 80% voted to keep the USSR in a poll in 1991. Do you honestly believe people in capitalist systems dont decide who gets what and who gets scraps? People in socialist countries usually have full time employment all their lives and free health care all their lives and free education, free child care, worker control and no living in debt or going told to go and attack other countries to steal their wealth, so which is more human?