A work environment so demanding that people keep leaving the company to seek better work/life balance is a feature, not a bug. Accounting is really not that hard, and neither are consulting, or banking, or law, or any of the other 100 hour week industries. If basically everyone can do their job competently then how do you decide who to promote to partner? The answer is to work all the juniors to the bone until most of them burn out and quit. Problem solved.