Let's be real. DOT should really be named Department of Highways and Roads. Expanding and building roads and highways and then moving our tax dollars year in and year out to the select few contractors who get these jobs every year.
My perception is that FDOT professionals don't actually set most of their priorities, elected officials (that includes the Legislature, Governor, Mayor and North Florida TPO) do. And since said elected officials have their pockets lined handsomely by developers and the construction/road building industries, it's no surprise whose bread they chose to butter.
Just look at the new interstates the legislature and governor have mandated that no one, including FDOT, asked for to line the western central and north sides of the State. And, consider that the head of FDOT is an appointed official, not a transportation professional, and you can understand the ongoing politicization of their priorities.
Overall, they have created a funding system that, institutionally, strongly favors interstate projects over any other transportation infrastructure (can you remember the last time there were no interstate projects in the area?). Local roads and mass transit suffer accordingly. The only time the system bends is when they absolutely have no alternatives left (e.g. there is no room to widen the interstates or add to their mileage).