Is the world becoming uninsurable?

The problem is the materials used. Greedy developers building junk homes and making bank. People in those areas are able to afford fire resistant housing but most of them are being swindled into buying stick homes. The few properly designed homes fared far better. Code needs to be updated and consumers need to be educated.

A number of those homes were old enough to qualify for social security. I doubt it's reasonable to believe developers could anticipate the environmental conditions that would befall a home some half-century since breaking ground.

I think the problem is less the materials used, and more that urban sprawl has pushed cities to build out into areas they shouldn't be building.

Destroying the wetlands to build houses closer to the ocean has eliminated the natural hurricane protection (from storm surge, at least) that many low lying areas had.

Building into fire-prone hills outside of cities in Southern California was never going to end well.