This is really interesting. I didn't realize the city had been trying to revitalize downtown since the 1970s. Can there still be hope at this point? I ask as a 30 year old who has never really seen downtown as anything but a few office buildings and a lot of empty storefronts...
Nearly any city of any size has been trying to bring back it's downtown since the '70s. That's is when the 'Malling of America' was in full swing. For years many tried to make DT into a mall, which is essentially what this master plan was seeking to do. Albeit, this particular plan was more unrealistic than most.
Over time, most cities came to realize that going back to what made Downtowns work in the first place, is what needed to be done. Trying to replicate a mall physically was a widespread mistake. Putting suburban style office parks in the urban DT was tried too, with little overall success.
Since the '90's, many cities, particularly the larger ones, have found the right formula. Jax is still way behind the curve on that though. The new plans for Met Park prove that, IMO.
Downtown can't be just retail, or office, or tourists venues, it has to be an integrated mix of many uses.
That 'formula', of course, is discussed in this forum non-stop.
So to answer your question, no, it is not too late. But it is getting tiresome waiting for someone with authority to actually see the light.