Much of Kotkin's writing about California is deceptive because he has a habit of ignoring one of the chief causes of California's problems: massive low-skilled immigration.
When you encounter a Kotkin column on California, first do a find for words containing "migr". If you don't find any, or the only mentions are in a supportive sense, then you know without even having to read the column that Kotkin is trying to deceive you.
Because of his habit of misleading by omission about such a vital issue, Kotkin is a favorite of supposed-conservatives that want to ignore the immigration issue (or that support massive immigration). Smearing California in order to promote red states like Texas is a bit of a cottage industry among supposed-conservatives, and many of those same people support massive immigration. Linking to or interviewing Kotkin is a safe choice for them: he's only going to confirm their incorrect beliefs.
See also the Fiscal Con page for examples of others ignoring immigration's impact on California.