The original undemocratic flaw is the artificial restriction of a two-party system. Further entrenching it by making the
10-20% turn-out primary elections even more decisive and using them to eliminate all third-parties in the general election is hardly a democratic improvement. You won't be surprised
who is significantly backing a measure like this.
On the other hand, it's the corrupt two-party system that makes closed primaries lose their persuasiveness; why should the only two effective choices voters have be decided in exclusive primaries? I voted no though the status quo is pretty bad. Instant run-off voting would be better, proportional representation more so. The U.S. electoral system is yet another thing tilted in favor of the wealthy and powerful.