The guards aren’t all changed out at once. The shift doesn’t happen immediately.
The people in charge, the ones making all the decisions, understand a tremendous number of things that the new hires don’t. They have value.
At the same time, the people in charge, the ones making all the decisions, probably don’t understand much about the new hires. They have fatal flaws and blind spots.
Some of these people at the top will move on naturally, others will be forced out. Their departure is neither good, nor bad, but progress requires change.
The problem is when an old guard, one who doesn’t get it, doesn’t want to get it, and doesn’t want to change, refuses to get out of the way and let the world keep moving forward.