You may be happy as Democrats that hundreds of thousands of Libertarian Party members and over a hundred thousand Green Party members are totally disenfranchised in the California vote, but try not to pretend that it's anything except massively scaled voter suppression.
In the sample ballots I saw there isn't a place to write in alternative/protest candidates for US Senate or Gov.
Upon further review, you are correct. I don't like that, either. OTOH, elections are about determining a winner so whenever the Greens, the Libertopians or anybody else gets into the top 2 during the primary they'll be on the ballot.
It's also the result of prop 14, a voter approved measure that has withstood court challenge.
https://en.wikipedia.org/wiki/Write..._Proposition_14_impact_on_write-in_candidates