Get rid of most of the existing managers and start with people who are experienced and qualified, who sincerely care about their employees, their professional development and work satisfaction. Hold managers accountable with reviews from their employees as well as co-workers and sanction, demote or terminate managers who cannot perform.
Challenge your managers to actually align with the corporate vision statements
Retain young talented employees
Aim for excellence not average
How about having HR present during interviews to help keep them unbiased.
Improve work life balance among managers. Ensure management salary is higher than in-scope employees in all cases
The crews need to mixed up....they get to complacent