The real problem isn't the legal doctrine of qualified immunity, but the informal doctrine of "police don't get prosecuted for crimes, and if they are, they don't get convicted."
Police probably shouldn't be sued for performing their duties. But the issue is that with a few choice words (I feared for my safety/life) their "duties" cover a wide array of actions that a lot of citizens would argue it shouldn't.
Example: There are many cases of Cops stepping in front of a moving vehicle when confronting a suspect, which then is used as a reason to shoot and kill the suspect because "their life was in danger". But it's very easy to argue that the Cop put their own life in danger by stepping in front of the vehicle. IMO, that should not be covered by qualified immunity, and yet it usually is.
Getting rid of qualified immunity wouldn't do jack squat to change that. The problem is an informal culture where police are not prosecuted (or if prosecuted, not convicted) for crimes.
Qualified immunity also applies to the officer who individually. The department can be sued still.
In this case, it doesn't apply because theft isn't part of an officer's regular duties. You can't sue an officer for taking your laptop and putting it in evidence. You can sue an officer for taking your laptop home.
Again, I agree with you that this should be true in principle, but I don't have faith that it will apply in this case, and this is contrary to the stated position of the police department.