To be fair, this is an unfair comparison, based on Jacksonville-the-city being Jacksonville-the-county. Of course Miami has less freeway miles per capita than Jax! How about Miami-Dade County, or "Miami" as the world sees it? And Washington DC barely has any actual freeways in its boundaries...but there's a whole bunch of 'em framing the area around the District that everyone thinks of as "Washington" if you don't live here, and which many people who live in those very 'burbs claim as "living in Washington."
If one was to do a fair, modern comparison, do either the county that the city is located in, or the MSA. I'm pretty sure Fort Lauderdale doesn't have all that many freeway lanes running through the city itself, but "Fort Lauderdale", otherwise known by its proper name as Broward County is highwayed up to the gills. The same is true of both Tampa and "Tampa" (Hillsborough County.)
This doesn't mean that the suburban, car-centric and dominant form that Metro Jax has taken is any less of a dead end for the metropolitan area. It just means that a bunch of cities didn't make the cut because the results used an arbitrary boundary (the city line) that pretty outmoded and outdated with regards to how people actually live and move through the "city" and the city. Especially in the South, at the very least, a county-to-county comparison would be more illuminating, as well as a MSA comparo. Or, to put this another way, my parents live and work in "Fort Lauderdale," and by that, I mean that they live and work in Broward County, which is just as screwed when the gas runs out as Jax. It just looks better on useless lists because of the city line drawn well before the county line.