There is nothing unethical about automatic processes and reducing your costs. Just like people are not unethical for choosing to pay less for tomatoes at one store than another, a business operator is not unethical for choosing to pay less for a certain task to be performed because they were able to automate it.

There is no reason a business has any responsibility to its employees outside of paying them for services performed in accordance with labor laws.

> There is nothing unethical about

Yes there is. Work is not just writing a paycheck and be done with it. It's more than that: it's working together towards a future that is better for all parties, in a sustainable way.