It’s not extracted it’s combined with labour to produce higher output than labour or capital on their own.
For example a worker with a shovel could only dig a small hole a day, but with the injection of capital (ie a backhoe) they can dig many more holes. The worker can increase their pay compared to what they would’ve made with just a shovel and the person that provided the backhoe can also generate a healthy return for their capital contribution.
Again, capital is extracted from labor. Who do you think built the back hoe? It didn’t fall off the back hoe tree. Workers built it, workers designed it. If some capitalist pig didn’t own it, then the laborers could just use it.
Even a labourer who has saved up can buy a back-ho. The backho could have been produced by a communist country or work co-op. Who produced the back-ho is not important.
The important thing is that value is stored, invested and combined with labour to make everyone better off. This is why wages are higher in countries with more capital such as the USA.
healthy return
How is it healthy that some rich investor gets to play golf all day because he can afford to buy backhoes and hire people to use them? How is it healthy that he earns more money if he pays them less, or that he alone is in charge of resources that a whole community worked to produce? What is healthy about any of this?
What you are describing is the entire fucking premise of socialism: workers cannot afford the means of production, so production ends up controlled by a handful of wealthy capitalists with perverse incentives and no loyalty to the rest of the human race. An entire tradition of thought is dedicated to how unhealthy that is.
