Without more qualifiers, that misses the point. Most local crops are still big ag varieties. The "local" crops you buy are likely the same ones sold in grocery stores anywhere in the US because so many things are grown in California.

But there are some things that can only be grown locally, because they aren't suited to shipping or because they have short shelf lives. And there are lots of varieties that are not on big ag's buy list, so large operations are very unlikely to grow them.

Even corn (which you mention) and soybeans need to be certain varieties to be turned into everything from high fructose corn syrup to the "shrimp shapes" made of soy I remember from grade school. They are part of the problem the GP is talking about, not the problem instead . . .

Big ag forces out diversity in crops and, frankly, forces a blander palate on the populace, who doesn't know better anymore.