Weed out bad cops from the force, incidents like we saw are unnecessary
Easier said than done. Before world+dog carried live cameras 24/7, any problem would basically boil down to the cop's word against whoever, and since the cop is notionally completely trustworthy (else he wouldn't be a cop) and the other person likely a perp (otherwise he wouldn't be nicked) it's obvious who is likely to be believed. The cop probably has backup from his colleagues too.
Also bear in mind that not every put upon person is playing a straight bat. Give your average tea leaf half and inch and he'll take all eight. The reason they are criminals is because they have no compunction about breaking the rules, so you'd expect a
lot of complaints about the police to be malicious and/or just trying it on because there's nothing to lose.
The big problem has been that genuine grievances just got lost in the noise of routine petty point scoring. The difference now is that when someone falls down the stairs we might get to see them being pushed or tripped, although there have been famous cases of such being caught on camera and nothing being done about it. However, those tended to be isolated incidents so easily passed off as just a bad apple thing, whereas currently we're seeing that there are far more of these apples than we imagined.