Policing either needs to adapt to modern day constraints or modern day constrains need to be neutered to allow prior day policing to keep up. The solution proposed here is the latter answser. The only way to solve with the former is to throw NSA style funding and recruiting at regular police work.
In the olden days if you wanted to find out what a group of criminals were up to you tapped their analog phones, bugged their houses when they were out, mayble rilfled through documents in drawers or you just sat at a table near them in a restaraunt. These things were easy because the only policing skills required were to have working ears and short term memory, you were up against criminals who had more or less the same skillset.
Current day policing is up against the skillset of the criminals and the skillset of those who make the tools that they use, so Police are up against criminal enterprise and also legitimate enterprise - as those legitimate enterprises now provide the tools which they use (yes, I know they don't specifically make them for this purpose).
Unless regular everyday policing budgets allow for them to employ staff who can intercept traffic OTA, who can MITM a 4G network or who can remotely read and decrypt device contents then the balance of skills has moved greatly.