Why is everything replace. Getting rid of the Fort Lauderdale -> Tampa and Orlando flights would free up airports for more long haul flights, where air travel excels. Intercity travel isn't a bit problem, but it's part of your sprawl problem. To fix sprawl, you need mass transit, which only really works in a hub and spoke model. When everyone worked downtown, mass transit worked to get people there, as we built cities around the car, we move out of expensive downtown areas, which broke mass transit, and brought us sprawl.
Intercity travel helps regional business, making it more practical to conduct with easy travel. Because trains are inside the city, that enhances the downtown (downtown Miami is now connected to Fort Lauderdale through West Palm via Tri Rail, plus Orlando, Tampa and other cities via high speed rail. That enhances the Miami downtown, which helps make mass transit MORE viable by making downtown office space more valuable. The more you enhance the hub, the more valuable it is to be on a spoke.
If 50% of Dade County worked in downtown Miami, mass transit is an easy solution. When people are spread out, you can't really do mass transit, just buses, and buses suck (slower than car because of stops, stuck with traffic with cars). Enhance the downtown cities and you will see more businesses there.
Older suburbs were established around a downtown with a train station into the major city. Modern suburbs become sprawling exurbs, where people don't enter the city.
If you want suburb -> city commutes resolved, you need to get the businesses back into a downtown area, which this helps. It's an extra reason to be in Miami if you are easy to reach for business if you can quickly come in from Naples/Tampa/Orlando.