That makes some sense, but it seems like a backward explanation for the bad worldbuilding.

Like, the lack of computer-aimed turrets. You might not want a completely AI powered ship, but this is more the difference between "cruise control" and manually controlling the vehicle. Not using computer-assist is basically risking your life. As we see in the movies, humans are pretty shit at using the turrets. Computer-assisted aim would mean the ship is much more likely to survive. And, if someone did manage to hack your turret, you could turn off the computer-assist like you'd turn off a malfunctioning cruise-control.

Also, if computer systems are hacked trivially by droids, why do they have hackable ports all over the star destroyer? Wouldn't they only put them next to human-guarded posts?

In addition, airgapped systems are a simple way to deal with this sort of thing. Like, your refrigerator or dishwasher probably has microprocessors, but they're not on the network, nor do they have a port you can plug into. Maybe there is one buried under a panel somewhere, but you don't have to worry about them being hacked.

And yes, droids are treated like slaves in some ways, but in other ways they're trusted to be bounty hunters, military troops, etc. If you trust / allow a droid to pilot a ship, why wouldn't you trust a turret to be equipped with computer-assisted aiming?