First you hire more selectively, slower, with higher "fit" requirements (talented, flexible, aligned with technical choices), and everyone are well motivated, so it just doesn't happen that often. You just accept that people vary, some will have better ideas, more productive, go through things, etc. and that's OK. People should not have to constantly stress about their day to day peformance that much. But when there is a problem, multiple people talk about it with the top leadership over time and then it's eventually handled the usual way.