Nah I’ve been on both sides of the fence. 9-5ers may reliably accomplish tasks through superior discipline, but they don’t do the heroics that really move individual teams forward.
The innovators in the company are likely correlated with doing more than 9-5. These people get frustrated that their ideas no longer get traction and leave the company.
Eventually what's left are the people happy to just deliver what their told without much extra thought. These people are probably more likely to just clock in the hours. Any remaining innovators now have another reason to become even more frustrated and leave.
Companies die when the sort of managers take over who see their job as to manage, taking pride in not knowing about the product or customers, instead of caring deeply about delivering a good product. The company may continue for years afterwards, but it’s a zombie, decaying from the inside.