Toledo and Rochester are two cities I've visited in the last decade that seemed to be DT Jax's siblings with what not to do. However, the both had the excuse of a declining population. I haven't been to either in a few years, so I don't know if they've changed.
Wow; not too familiar with those two cities, but Jax is gaining in population so there shouldn't be an excuse. However, that population gain could be illusory owing to consolidation (whole county being Jax except for a few towns that opted out); i.e., the old city limits, boundaries, and the immediate areas in and around downtown are wholly not doing so well, so it could explain why those areas in and around the urban core are not doing well and just not responding (owe it also to our inept government leaders and administration). Curry seems to think we're doing just fine; I don't think so. We soon shall see, if we're not nuked, a few years from now. Hope the economy and/or a major recession doesn't take hold anytime soon.
The old city limits have declined by 50% since 1950. So, yes, without consolidation, it would be a rust belt city style decline. A challenge locally is that "any" development is seen as a great success, despite economic conditions that should easily stimulate three times as much redevelopment as we're currently witnessing. In addition, since there is no vision of what true urban vibrancy is or even how to get there, we're overlooking the importance of small "glue type" public realm projects that help cluster, complementing developments together at a compact pedestrian scale level. These are the things that can quickly change the overall image and generate consistent foot traffic in a more efficient manner.
Here is an example:
Before - 2009 Giralda Plaza in Coral Gables

After - 2019 Giralda Plaza in Coral Gables

Full article:
https://www.thejaxsonmag.com/article/rethinking-adams-street-the-makeover-of-giralda-plaza/