A jury of your peers used to mean exactly that - people who were familiar with you, the social circumstances that lead to your being in the dock, who had empathy both for you and for the law. Part of the tradition comes from the Frankpledge and tythings, which required you and your peers to collectively police one another, and endure collective punishment if you failed in your duty to justice. In addition, early juries were responsible for investigating the purported crime themselves, and were allowed to acquire information for themselves.
This of course all lead to a degree of corruption (in fact, significant corruption in later years), but was potentially an ultimately fairer system, less biased in favour of conviction.
Having a jury prevaricate on the outcome of a trial concerning someone who comes from a different world to them, who don't understand the nuance of the reality that faces them, who are not allowed to educate themselves about legal facts or the facts of the charges, frankly beggars belief - but it's what we have.