Weeding out the officers that would commit infractions that result in civil suits will probably also weed out those that would actual commit a more serious crime.
If one of the 18 use of force complaints against Chauvin had also resulted in a civil lawsuit that found Chauvin liable, he might have been removed from the force earlier.
That's one theory at least—I think it's a reasonable one.
I don't think removing QI from police officers should be the end-state of reform, but I think it's a necessary step and a good one.
But you are right that civil suits can also be filed for serious crimes.
- steals $200K from you - has their attack dog bite you you while your calmly sitting down and handcuffed - serve a warrant for someone they already have in custody by breaking down your door in plainclothes without announcing themselves and then shoot your girlfriend eight times.
(These are all real cases from this year, where the courts rules there was not grounds to sue because of qualified immunity)
Now, you can at least sue them for such actions. I suspect the damages will be paid for by an insurance policy taxpayers paid for. Still, it is better than the current situation. At least such officers will be a financial liability for their departments.