Peter Drucker is attributed with first putting it this way: "Culture eats strategy for breakfast". Well said. How does one execute strategy when culture doesn't comply? Tough job, for sure!
Firstly, in my experience, whenever a company or an organization tries to change something they rarely are able to do so without one or more trustworthy people inside the company leading the way.
If change is sought by someone without sufficient trust, "change" remains wishful thinking. Why? Simply because only a trusted leader is in a position to challenge culture and tradition(s).
Secondly, because very few companies have such leaders, or because it's just too darn hard work, objective outside consultants are hired to do the job. E.g people like me.
However, and this is my point, even though I am a consultant hired to facilitate change and improvement, I'm still of the opinion that such processes are best led by the leader i-n-s-i-d-e the company, if possible. Are you a trusted leader? How do you know when someone is..?! Would you agree that this is a vital question to ask the very moment any desired change is defined?