Ryan Williamson has this op-ed in the Orange County Register about the California top-two system. He says that California’s legislature has become more polarized under top-two than it was in the past, and that California’s legislature is more polarized than Congress.
He also suggests that California replace it with a top-five system. He doesn’t explore other alternatives, such as the Louisiana system in which there is no primary; or restoring party nominations combined with ranked choice voting. His op-ed is marred by his misuse of the term “blanket primary”. “Blanket primary” is defined in political science textbooks as the system California and Washington used in the past. All candidates ran on a single primary ballot, but the top vote-getter from each party then ran in the general election. Thanks to Fairvote for the link.