Each issue affects the other, and what is needed is some strategy or set of approaches that make each one ‘better’ at the same time, creating virtuous—not vicious—cycles between the three.
Your leadership bench strength issue is affecting your culture. Your culture is affected by your leaders, many would argue shaped by them. Your ability to change at the required pace is made or broken by your culture and your leaders.
We believe you have to start with strengthening those who lead and manage others. Start with leadership development, and then use that strengthened population to shape your culture and improve your ability to change. If you start in any other place, you will fail.