Perhaps worth pointing out for general awareness that trial by jury has nothing to do with democracy, per se. Not all democracies do it, and it was (is) a pretty unique thing about the American system of checks and balances at the time it was enshrined in the sixth and seventh Amendments of our Constitution. Jury trials can exist with or without democracy.
To your point about different time and place, yes, but that’s the system: the jury you get, absent a mistrial, is the jury you get and their opinion is what decides what you deserve by definition (absent new evidence, appeals, etc, within the confines of sentencing regulation, etc.).
Perhaps what you’re after is that there’s no universally objective standard of what a person deserves for their actions, given all the myriad influences and conditions that lead to a particular moment in a person’s life, and which may lessen that persons agency. Therefore the judgement of society is imperfect in the sense that it cannot adequately grasp all these attributes, and may give attributes differing weight based on something as small as whether their eggs were over cooked that morning. So for a person to use the word “deserves” with authority is flawed because a person or people cannot render a perfectly objective judgement.
I think you’ll find that this is an argument as old as time, but whether by birth or immigration, people living in a system operate by its rules, and the word “deserve” reflects the authority of a society to bring down punishment on scofflaws. Like when I tell you something is “cold” we need not debate the true principle of what cold means, you assume to context. So should you assume context for the word “deserves”. Society has never achieved perfection in balancing agency and justice but herein lies a predictable truism - if you run around with a band stabbing others so severely that some die and by luck some don’t, society will determine ya dun f’d up.