Well, that is if you are the right kind of person.
The reality for most people who encounter the justice system is that they are presumed guilty from the moment the police begin the investigation right through sentencing. If you are black or indigenous you are presumed guilty. If you are poor you are presumed guilty. If you are poorly educated you are presumed guilty. If you have a developmental disability you are presumed guilty. If you are a woman who says a man sexually assaulted her then you are presumed guilty of perjury.
Who is presumed innocent? Jian Ghomeshi is. Bill Cosby is. Nigel Wright is. George Zimmerman is. The RCMP officers who shocked Robert Dziekanski to death are. Police who kill young black men are.
A lot of people say presumption of innocence is important because "the state" would otherwise abuse its power to lay spurious charges against political enemies. Go ask all the 200-some people who went to prison for killing children on the evidence of Ontario's doctor Charles Smith over a 20 year period what happens when the "the state" comes down on you. Go ask them how much the presumption of evidence is worth.
To defend the idea that presumption of innocence is necessary to protect us from the state, you have to defend the idea of a state that would lock up its political enemies if the rules allow it to but that would recoil in shock and the idea of fabricating evidence, or charging you with crimes completely unrelated to what they are really upset about, or putting you on an extrajudicial kill list to be taken out by drones. You have to defend the idea that by getting into a Red Queen race against the justice system, the individual will somehow be empowered rather than swallowed.
Presumption of innocence isn't going to change, and I'm not advocating that we change it. It would be too hard and too disruptive. What I am saying is that it is stupid, it doesn't actually do any of the good things that we pretend it does, and it is just an excuse for giving the wealthy immunity from criminal prosecution. I don't think we can change it, I just don't want to hear it talked up like it's a good thing anymore. We ought to be ashamed of ourselves.