Cops CANNOT protect every individual perfectly - that is preposterous and impossible (hence RKBA) - but they can do their level best to protect as many individuals as they can, which sometimes means letting some suffer harm while ensuring a greater number do not. Call it triage, call it quality assurance - realistically, you can't have perfect service in every instance.
Your gripe amounts to buying a popular product which turns out to be defective (a normal statistical occurence) and blaming the manufacturer of "false and deceptive advertising". The guarantee stamped on the box does NOT mean that the product absolutely positively will work.
You get what you pay for. You - personally - are not paying much for police protection. What you get for that money is pretty good. If you want better, hire a bodyguard ... and be prepared to pay far more.
Paying little and being appalled at not getting much (regardless of what's stamped on the box) shows a lack of understanding of reality.
I am not complaining that I don't get much from the police. What I get from them I do not want (revenue enhancement), and what others get from them, by and large, I don't want either (no-knock raids, paramilitary assault squads, kids arrested for having a toy gun on their key chain). We made it more than 100 years in this country without a modern police force, and I think law enforcement and justice in general were more capably administered back then.