I have had periods in my career when I performed poorly, and in virtually all cases the cause had nothing whatsoever to do with the job environment or management. (The real causes included depression and poor coping mechanisms for it, a toxic relationship, and the birth of a child.)

If an employee who has a good track record is going through a period of personal or family-related issues, the employer should support them through that (and not just via FMLA). Not just morally, but also for long-term organizational health. This too is part of the work environment.

Are we building something for the next 6-12 months, or are we aiming to build a monument that will outlast our careers? Sometimes the answer really is the former, but it has very serious costs that are often unaccounted for.