Near the end of the occupation their refugee space ships seem to lack even warp drive.
But everybody at the time thought these ships did have warp drive. Otherwise, the Cardassians couldn't have constructed their nefarious "Ensign Ro" plot so that it required said ships to have warp drive!
No, Orta's particular ship must have been warp-capable - the drive just happened to be broken, which the Cardassians didn't anticipate.
At the end of the Occupation, Bajor is immediately shown operating all sorts of warpships, including the specific ship type we saw in "Ensign Ro". We don't know how old that technology is, or where it originates, but we have every reason to think that Bajor
during the occupation was perfectly warp-capable. We just don't know how long before the occupation this capability was attained.
Also I submit that Bajor was far worse shape than Earth after WWIII. There were no formal technological or science institutions to support the advanced infrastructure necessary for post scarcity economics.
Why wouldn't there be? Cardassians were never said to have slaughtered the intellectual classes, or anything like that. The institutions that may or may not have been suppressed during the occupation could have sprung back to operation essentially overnight. Better, certainly, than the corresponding institutions on Earth after the devastation of WWIII. Cardassians weren't said to have devastated anything, either, after all.
As for slavery, you're right, it doesn't make much sense economically. However, if an oppressor actually enjoys enslaving someone, then it can and will happen.
On that vein, I'd argue that the Cardassians were never using slave labor as such. Instead, they had prison camps where the inmates were used for forced labor - but the purpose of the camps was not to produce stuff, it was to keep the inmates occupied, oppressed and possibly obliterated (although the only party suggesting that the camps were for genocide was a Cardassian liar!).
Bajorans working on actual productive endeavors were not indicated to be slaves. The industrial workers on DS9 may or may not have been paid - this was never commented on. But there was no comment on them being slaves, either. The only people on DS9 actually labeled as slaves were the comfort women, and we don't exactly know whether that Bajoran label was accurate.
Bajor was shown to be in complete shambles after the occupation. Basic necessities were lacking.
Umm... The only necessity we saw lacking was a steady supply of power - Quark suffered from a brownout during his surface visit in one of the early episodes. The mentions of food shortages and whatever were in relation to the actual duration of the occupation - and even there, they seemed to only affect specific people, those in Cardassian disfavor.
Cardassians didn't have time to devastate much when they received their orders to withdraw. They thrashed DS9, and didn't do a very good job at it. They salted some fields, the issue in "Shakaar". But they didn't blow up the city halls or power stations, or anything like that - not to our best knowledge.
What damage the actual occupation process did is not specified. Bajor was stripmined, that much we know - but that need not have distressed the world much.
Really, "starving people on Bajor"? Where? When? Who? We never actually saw a hungry Bajoran person after the end of the occupation.
Timo Saloniemi