It's difficult to believe that the decision should be made quickly. When making decisions about the trajectory of someone's life, they should be made with care. Having a system that removes snap judgements and bias is important, and I would say that even a quick-scan and re-ordering of documents is a form of bias.
Having interacted with the criminal justice system, that's the view they seem to take.
1) Most people charged with a crime these day are usually guilty of it. The public has made it pretty clear they would rather see no one charged if the crime is a legit whodunit -- no one desires to see innocent people arrested and charged just to give the impression of safety. Prosecutors, and downwards (police) feel pressure to only file and prosecute cases that are legitimately believed to be of truth regarding the suspect. That said, you are innocent until proven guilty. The burden of proof is on the state. Even if we can mostly feel that you did it, if it can not be put before a jury to return a guilty verdict, you are not to face penalty in our society (mostly; ignore OJ's civil case... that's a pretty rare exception to be honest).
2) I understand why judges seem automatic -- but remember this: in a criminal trial (minus your option to do a bench trial), you are found guilty or not-guilty by a jury of your (location) peers. The judge has his own opinion, but he is restricted based on the guilty/not-guilty finding of the jury, and sometimes state/federal sentencing guidelines. Of course there are prick judges who SENTENCEMAXXXX people just to be an asshole - no one with an ounce of common sense will endorse that. In general, I trust and expect judges to apply their experience of both law and life in determining what is the appropriate penalty after someone is found guilty.
So no trial, no presumption of innocence, and absolutely no interest in anything other that processing 'criminals' as quickly as possible.
So your comment "Most people charged with a crime these day are usually guilty of it"
May well be true. the issue is that it is self reinforcing, most people are guilty, so the system treats you as probably guilty, so the people that aren't guilty don't get the protections theyre supposed to have the right to.