If they don't matter at all, there's tons of steep lots you can buy in the hills for like 10-50k with neighboring houses in the mid-to-high millions. People say they're unbuildable but apparently there's no such thing?
More seriously, I generally agree with most what you're saying. It should be easier to increase density in Los Angeles. By-right ADUs & JADUs, 4-unit TIC conversions, transit-oriented dvelopment are all a good start. We should do more. I shouldn't see anything but the back of apartment buildings from my window on the Expo line. 500k people should live in DTLA. Wilshire should look like Tokyo as soon as the train is done.
It's just weird to bring this energy to such a tragic situation. I don't think you could honestly say Altadena and the Palisades were the top two areas you'd focus on increasing density prior to Jan 7. They're no closer, nor easier to connect to transit, nor less fire-prone today than they were then. Most of the SFH that was destroyed in the Palisades were $3-9m[1] houses on 1/8th acre lots i.e. doing a pretty good job paying their own way on their infrastructure. The insurance stuff is going to be a pain, but I expect the prospective-risk model that was just authorized will force homeowners to bear more of their risk (and thereby apply some market forces to land-use decisions in the rebuild). And if the highest-GDP county in the highest-GDP state in the county needs, for once, a bit of Federal help it'd be hard to characterize that as unfair.
To focus on them as a place to enact specific parts of your urban-design vision (however good it is!) feels just as exploitive as 'investors' trying to buy lots cheaply to remake in the image _they_ prefer. These are our friends and neighbors, victims of a disaster. We should help them rebuild as quickly and prudently as possible, so we all can continue pulling the city toward a denser, safer, healthier future.
[1]: yes yes some prop 13 bases in there that I'm approximating away sue me.