No, it's not. California has eliminated primaries in the usual sense (what is called a “primary”, outside of Presidential nominations, in California is the first round of a two-round majority-runoff general election where you aren't allowed to win outright on the first ballot even with a clear majority), and yet here we are talking about the effect in California, so partisan primaries can not be the issue. We’ve ruled that out by not having them.
The issue is FPTP single-member district legislative elections, which supports partisan duopoly and narrows the meaningful space of political debate toward a single high-salience axis and issues where splits align well with that axis, marginalizing all other issues. This has been somewhat extensively studied in comparative study of modern representative democratic systems, see, e.g., Lijphart’s Patterns of Democracy.