What about municipal PDs is troublesome to you?

No training standards, not larger-scale oversight, a lot of "we have always done it like this here", a lot of "I know the DA and the judge because we go to the same BBQs", incentives to contribute to the (very local and therefore very noticeable) general fund through fines and civil forfeiture, the list goes on. Basically a police that is the strongest gang in town rather than a professional and slightly anonymous representation of the law. Which in the end makes it less likely that the law applies the same to all, irrespective of the person.

Mostly the local oversight of the local force. The overly cozy arrangement just invites corruption.