Personally, I think it's generally much more worthwhile to invest in making the service better than in eliminating fares. Removing fares often doesn't help with ridership unless the service is sufficient (like it is in decent portions of DC) to make the opportunity cost for riding lower than that of driving, and I'm not sure that's true for most people in Jacksonville. Bus routes are too slow without enough dedicated lanes, we don't have any faster trunk rail lines to feed buses off of, development patterns are a disaster that make trips long and difficult, while parking is cheap and plentiful with constant highway expansion. Those patterns have to be changed to support substantive ridership increases under fare-free systems.
A lot of fare-free programs ultimately pull walkers and bike riders onto unimproved transit networks instead of drivers, and Jacksonville probably doesn't have a big enough base of walkers and bike riders to make that effect happen either. Another problem is that the logic of fare-free programs generally relies on public officials making the consideration to actively support transit in their city instead of passively tolerating it, and I'm not sure Jacksonville's officials are going to do that, especially when we're talking about bus lines and not fixed infrastructure like the Skyway.
I will grant you that JTA has plans to study fare-free programs in FY 2024 so it's possible they'll be convinced otherwise. Also that according to JTA's most recent budget, they currently make about $9 million from fares, ~$7 million of that from bus operations, which is slightly more than their federal preventative maintenance funding but definitely a fraction of the $136 million budgeted to actually run the bus system. But I'm not sure how much faith I have in the city or state to fill that gap if the choice was made to go fare-free.