> The resources used to make those arrests could have been used instead to investigate and prosecute the perpetrators identified by those rape kits.

In theory, yes. In practice, no, they couldn't, because police officers aren't generally qualified to be processing and/or investigating rape kits.

We can't even say that they should have hired fewer officers and spent the money on people qualified to investigate these cases instead, because the LEO unions ensure that those cops stay employed (and also explicitly lobby for drug criminalization so that those officers have work to do).

EDIT clarified "criminalization" wording