The people making the decisions have no training in law at all, yet they have to decide if the law was broken. They get a brief spoken explanation of the law, but only after they have been given the testimony. Why would you not have someone trained in the law decide if the law was broken? Why would you not allow the jury to interrogate the witnesses when they must bear the responsibility of the decision? The idea seems to be that random people off the street will somehow be more willing to consider all angles and if they disagree, you get another random sampling and try again. Try enough times and eventually you'll get a bunch of people who are annoyed enough by being forced into jury duty to just agree so they can go home. Real justice right there.
You might say that the jury system allows for a justice even if the judge is compromised. But obviously it doesn't - the judge controls what information can be fed to the jury and the jury must make the decision based off that evidence. If the judge is biased, the jury will be forced into a particular decision anyway. Why not just have the judge do their job and have an appeals system and punishments on the judge for bad decisions? And yes, that system works fine. See the current Oscar Pistorius trial for a working system (imo).