As a multiple brand truck
As a multiple brand truck owner, I've owned 3 Toyota pickup trucks over the years going back to the mid 80s. In our region, Cal Trans and O-Dot do not salt the roads in winter. So I haven't experienced frame rot. My immediate neighbor drives a 1996 Toyota 4-runner with 300,000 + miles on the odometer. It's here daily driver. And, outside of normal maintenance, has required ZERO major mechanical or aesthetic repairs. This would appear to be a regional issue. and yes, a body off frame replacement is possible, although generally not cost effective.
Should a manufacturer be held accountable for a near 20-year old frame? Hell no. Cheers!