Of course some[0] don't earn their wealth, but their wealth was earned by someone else still providing value. They got the output for nothing, but it was still earned.
There are some people, such as Vladimir Putin, who just drain their country of its resources, enabled by the force of the state. But capitalism is about free exchange of value. So if someone gets rich; lots of other people got value.
[0] https://en.wikipedia.org/wiki/List_of_female_billionaires#20...
This is only true sometimes. You can, in many cases, create a functional monopoly and force people to pay you for their essentials. You can provide them a useful product, but deny them a better alternative that would make you less money (the old super strong drinking glass example). You can make use of the fact that value doesn’t mean “rationally determined to be of utility” to sell people things that are damaging to them for huge amounts of money. “Value provision” just means “you give me money for any reason,” and there’s a lot of shitty reasons people have to fork over their money in capitalism.
This is all tangential to the idea that "capitalism only makes people rich if they provide loads of value to others".
The heir who doess not work, and who has never worked, often the same being true of their parents, and their parent's parents, is eating food grown by the labor of others and so on. There are those that work, and there is also a parasitic rentier class who does not work.