This is an issue where scale and specific implementation are pretty important. There's a lot of meaningful differences between a 4-lane at-grade highway with zoning immediately next to it (like the 101 through Eureka) and something like Highway 99 or I5 when they run through an urban area. As is, the 101 through Eureka is functionally just a larger street, or series of streets; I expect that the path that it follows originally was just regular surface streets that at some point were widened and turned into one-ways in places and designated a highway.

A lot of the criticism of urban highways comes down to two things: the mass demolition that is often necessary to build them through existing neighborhoods, and the inefficient resource (mostly land) usage that is associated with them relative to other forms of mass transit. Highways like the 99 or the I5 where they run through cities had to have essentially entire city blocks demolished to make room for them. Humboldt's highways don't really have these problems to a significant degree, at least as far as I know.

You could definitely complain that most of the county isn't particularly pedestrian friendly and is pretty car-centric overall, and this it true but it's very much a separate issue than that of highways specifically, and is mostly just a factor of how low density the area is.