Yes, yes, large numbers of jurors are fools, just like large sections of the population are (how else to explain the Labour Party?).
And yes, most certainly, it would be more efficient to have it all done by judges and magistrates and never the common people get a look see.
However, at root here, we’re talking about freedom and liberty. Things which are not entirely amenable to that pure efficiency argument.
And the real, ultimate, power that juries have is the ability to say:
“Yup, bang to rights, you’ve proved he did it, guilty as sin of the accusation. However, fuck off matey for that shouldn’t be a crime. Not Guilty!”
This is rare, I agree. Perhaps so rare as to be almost unknown.
Yet I know of one case in my own adult lifetime where this did indeed happen. And it led to the wholesale rewriting of the Offical Secrets Act too. For the citizen jury clearly and obviously (although we’re not really supposed to say so, for the defendant was found not guilty and was thus not guilty as sin) said that yes, the law says that that is a crime and we don’t think it should be. Fuck off.
And that is the real point of the jury system. It’s the final bulwark between us, the citizenry, and those who rule us. And that’s why it should not be abolished. For abolition would leave us entirely naked and defenceless against the political classes.
A fate which the history of certain other countries has shown us is one not to be desired.