None of the successive reforms made since 1968 has produced a perfect system, and in a nation of this size none can.
A national primary would penalize all but a few nationally known candidates. Caucuses tend to favor candidates with constituencies of well-organized voters. Reasonable people can differ about whether it’s fairer to allocate delegate proportionately or by winner-take-all.
Arguments over the rules inspired one of my Rules of Life which is: “All process arguments are insincere, including this one.” A loser’s real gripe is not with the process but the result.