That's definitely true of industrial resources. But food?
Let's assume that there's not enough room or whatever on Cardassia Prime to build the needed arcologies to feed the planet's population. How many orbital space farms would you need to make up the difference? How much energy would you need to power the transporters that send the produce down to the surface (and recycled fertilizers back up)? How many people would you need to employ to keep it all running?
Now. How much of that do you think you could build for the same cost as a single Jaldun cruiser?
My interpretation is that the Cardassians did, in the not-too-distant past, have a legitimate food crisis due to a series of ruinous internal and external wars that wrecked their production. But now that they're unified under a single government and not embroiled in an existential conflict, there is no good reason for them to still be hungry.
My take on it is that the Cardassians
choose not to develop agricultural infrastructure on their capital world, even though they could. Because centralizing heavy industry on the homeworld while "outsourcing" farming to isolated colony planets creates an inherent mechanism of political control. Like a demented version of checks and balances.
The homeworld population is numerically dominant and none of the colonies is economically sustainable without them, making a frontier colonial rebellion nearly impossible.
Conversely, the homeworld population starves without the flow of provisions and resources from the frontier- and this flow is susceptible to whoever controls the navy and the merchant marine. So a large scale popular uprising on Cardassia Prime is
also nearly impossible, because it would start to run out of food in short order.
The ground forces and the Obsidian Order, meanwhile, can seize the highly centralized economic and industrial infrastructure that supports the fleet, neutralizing the fleet as a long-term threat in the hypothetical event of a large scale fleet uprising. Sure, it'd mean a lot of starvation on the homeworld, but the army and secret police don't have to worry about that directly as long as they can confiscate enough of the food to feed
themselves.
So the homeworld population has its hand on the colonies' neck, the navy has its hand on the homeworld population's neck, and the army and Obsidian Order have their hands on the navy's neck.
...
However, as a side effect, the Cardassians
actually have a real economic problem. In that they've got a relatively inefficient mechanism for feeding their homeworld, and one that leads to disaster in case anything really bad happens to the Cardassian infrastructure.
To make matters worse, they can't fix the problem without finding a governmental structure that runs on something other than rule by terror and autocracy. Because right now, suppose they make the attempt to solve this problem (by bringing more food production to the homeworld, by decentralizing industry, and so on). That would destabilize the system of 'checks and balances' by which any of the state's major power blocs can exert force against the other power blocs.
If the homeworld becomes self-sufficient in food, that signals to the fleet that the rest of the government may be preparing for some sort of purge of the fleet, and is taking precautions to prevent the fleet from having the power to retaliate in self-defense.
If industry is decentralized, it looks like a bid by the fleet to turn the colonies (currently tightly dominated from Cardassia Prime) into a looser network of frontier satrapies... Which the fleet can then 'spin off' into independent political entities.
And so on.
Honestly, if it gets to that point, I don't want to end the war with the Cardassian Union.
I would want to end it by negotiations with the Union's successor states.
Again, don't bet on the Federation actually being willing to go that far. In canon, the only reason the Cardassian Union broke up was because its government had already been crushed by the weight of the Dominion. The Federation simply moved into a power vacuum.
There's no reason to expect that to change. So expecting us to be able to break up the Union, when everyone we know of who has the power to negotiate
is themselves a Union official, would require far more willingness to punish the Cardassian people and occupy their territory than I'd expect.
Quite frankly, I'm not sure we should even want this. A war fought with Cardassia over colony worlds, the independence of affiliates, and the relative strength of the fleets... There'll be dying, but with any luck at all the dying will involve the military and relatively lightly populated planets. By contrast, actually breaking up the Union will require wars of occupation on multiple planets, with heavy ground combat.
I'd rather fight a war that kills two million people every twenty years for the next century, than fight
ONE war that kills fifty million people right now.