Brilliance of Lawyers and Judges

Juries are triers of fact; judges are triers of law (and they are triers of fact in the absence of a jury).

I have no idea what the remainder of your post is trying to say, but English-derived law (which American and Canadian law both come from) uses the principle of stare decisis. Essentially, if there is a precedent, it is to be followed. Conflicts arise when precedents are unclear or they conflict with each other, or they haven't been made yet. When computers were first invented, there was no such thing as computer law, for example. Hence precedent was more analogous. If something looked like slander, then slander precedent was used, etc.

Scalia was a very intelligent man. But I also went to school with a lot of people who weren't so brilliant. Many of them passed the bar, too, and have had careers in the law. Not every lawyer is a genius. Far from it. The discipline is difficult but it comes down to passing the bar exam, when all is said and done.