This is a side-effect of police militarization that doesn't get much attention from its critics: using advanced military equipment should also require advanced military training. Local police agencies that receive all this new military-spec equipment don't always get (or more likely, never get) the funding for necessary training on how to use it. Much less does such training really exist since this stuff was all designed for use in actual war zones. The extant training materials would inherently be oriented around that type of usage.

Even the worst part of the worst city in the USA could not be more different than a war-stricken area of Iraq or any other region where military action is a common occurrence (other than that they probably contain more friendlies than enemies).

Aside: It is truly sickening that they used a flashbang on a residential house where they hoped to apprehend a single, low-value suspect that could not possibly have been that well armed. Again, lack of proper training.