FEMA had large amounts of food, water & generators pre-positioned on the island prior to landfall for immediate distribution. Trump initiated disaster declarations for Puerto Rico and the Virgin Islands prior to landfall to allow federal funding to be available immediately.
The main reason it took a few days for commercial airline traffic to be able to get to and leave Puerto Rico was because FEMA and other federal agencies were using the airport to help in relief efforts.
The people complaining about the Jones Act were either ignoring, or didn't know, American ships were getting supplies to the island. The hold up was getting the items distributed once in port. Adding more ships to the equating wouldn't help. I do believe, though, that Trump should have handled this differently for PR purposes if nothing else(I'm aware the Act was temporarily lifted this morning).
Thousands of federal workers and people representing various charities are on the ground helping as we speak and have been there all along.
We have to keep in mind, this isn't a drive to Texas or Florida, things may not happen as quickly as the Puerto Rican people need or as quickly as we'd like to see happen. The devastation there is enormous. It is a terrible situation that I believe is being handled about as well as it can be. As with anything, there will be mistakes and lessons learned.
Trump appears insensitive because, honestly, he is insensitive. But this isn't the gross negligence it is being made out to be.