All getting well paid .. are they getting any equity? Do they make more (meaningfully more) money if they do a good job? What incentives do they have to do a better job other than not being fired?

Are you sure of the reasons why their performance is bad? Are you sure it is not the case that you are giving them bad instructions, and they are following them as best they can, but because the instructions are bad the overall product is bad, and when you ask them about it, they decide to agree with you that their performance is bad, rather than telling you the truth that it is all your fault, because they don't want to anger you and risk getting fired?