I am a lifelong Floridian and have lived in South Florida for over 35 years. I lived through Andrew, Wilma and Irma. I am also in Search and Rescue and have done damage assessments after a number of storms including Katrina and Charlie and others. I am also an Engineer intimately familiar with the damage that wind and water can do and have spent the better part of my life designing to mitigate them.
Having said all that, this was a tough storm to call. Direction and wind speed changed a lot. It would have been prudent to ask people to leave early but Emergency Managers have to worry about putting too many people on evacuation routes at the same time. They also have to worry about being "chicken little". Most people will evacuate needlessly once or twice before you lose credibility with them and they will never heed a warning again. I believe this thinking keeps EMs from being overly cautious with early evacuation orders. It is a fine line to draw and for obvious reasons, can backfire.
I probably would have evacuated the barrier islands earlier but I have a hard time being overly critical of the decision makers that didn't. I have been in the cone dozens of times in my life. Of those times, maybe three have been close enough to warrant evacuations in my area. They turn away or peter out more often than they come right at you.
It is a lot tougher than people think