The problem is that California very frequently gets into situations where there's a legislative supermajority on the opposite side of the issue from the general public. Just this cycle, AB5 passed the Assembly with 76%, and ACA 5 (the subject of Prop 16) passed with 81%. If the legislature were allowed to repeal ballot propositions, they'd do it in a heartbeat, and the will of the voters would not end up being expressed.