The Daily Mail reports a survey Volvo did to learn the most hated roads in the US, three are in CA. I write in defense of two of them.
The three are US 101, I-5 and I-405. 405 is mostly urban and it is the urban parts of 101 and 5 that are disliked when they become overcrowded or backed up by an accident or spill.
On the other hand, large parts of both 101 and 5 are rural, and generally pleasant to drive. Driving north, 101 becomes mostly rural somewhere around Camarillo and remains so until you pass Carpinteria, then on the far side of the Montecito-Santa Barbara-Goleta complex it is largely rural again until you reach Gilroy south of San Jose. 101 is a mess through the Bay Area while north of Santa Rosa it is mostly rural all the way to Seattle. A lot of this is quite scenic coast range and shoreline terrain, surfers are common and I've seen a pod of porpoises twice.
I-5 is a mess in greater Los Angeles, but becomes rural beginning just north of Santa Clarita and remains so until the Stockton-Lodi-Sacramento complex is reached. North of Sacramento, it is again rural until Portland. 5 in CA is less scenic unless you enjoy cultivated fields and orchards, but it's faster than 101. Watch out for dense fog in midwinter, following rains.
Most of my life was spent in CA and I was fortunate to do most of my driving on 101 and 5 on the rural stretches between Sacramento or the Bay Area south to Santa Barbara. Traffic jams were very rare and maintaining 65 mph a snap. I miss driving 101 between the Bay Area and LA, much of which is quite scenic.
During the 50+ years I drove an RV I tried to pass through the LA area on Sunday morning when most Angelenos were sleeping in. Otherwise, the whole LA basin was mostly an overcrowded mess.