They are expected to grow to one-fourth of the nation's population by the year 2050. The nation is now made up of poor and wealthy, white and black, Muslim and Buddhist, Haitian and Indian, Anglo and Cuban. Not only that, women have as much clout as men. Jefferson and Madison would be shaking their heads. The mandate for unanimous juries also opens the window for unjust verdicts, whether influenced by corruption or whackos that can't be identified during the selection process.
Irish juries rely on majority verdicts only.
Same with Switzerland and others. Denmark requires eight of twelve. Sweden and Finland have scrubbed civilian juries in favor of professionally educated citizens who assist judges in reaching a just verdict. Poland uses a system of one judge and two lay magistrates. The United States in 2000 is not the same country founded in 1789.