Western law is founded on a presumption of innocence. Police are only shooting criminals if they wait to draw their guns until after the suspect has been arrested, charged, tried, and found guilty.
Until those things have happened, they are only able to shoot civilians (or each other) - the one exception being pursuit of convicts engaged in a prison break-out.
Summary execution without trial should not occur in a nation that aspires to become civilised.
You missed the category of person called "Suspect". You are correct that all people are presumed innocent... and the part you missed is the part that goes... until there is probable cause to suspect the person has broken or is breaking the law... that is called a Suspect. Cops shoot Suspects that are perceived to be a danger to others. They don't shoot "civilians"... they don't shoot convicted crimminals... they potentially shoot Suspects.
Suspects are a subset of civilians, not a subset of criminals. The only way for a suspect to become a criminal is via a court of law. Suspects have the exact same rights as other civilians. Including the right to be protected and served by the police.
That the number of innocent civilians killed by police (who categorize them as 'suspects') is FAR too high in the US can be easily seen by comparing the proportion of such of killings in the US with the proportion in other jurisdictions. In the rest of the world, it is not a routine matter for suspects to be killed by cops. If the rest of the world can arrest and bring to trial these suspects, then so could the USA, if only they would stop summarily executing them instead.
Judge Dredd is intended as a satire, not a 'how to' guide.