Having worked with both good and bad QA...

The biggest determinant is company culture and treating QA as an integral part of the team, and hiring QA that understands the expectation thereof. In addition, having regular 1:1s both with the TL and EM to help them keep integrated with the team, provide training and development, and make sure they're getting the environment in which they can be good QA.

And work to onboard bad QA just as we would a developer who is not able to meet expectations.