The Sears kit wasn’t unique in that regard and they were built pretty good for the time. Non kit houses were often balloon framed or featured other serious code issues.

I live in a northeast city, and the average house in a ten block radius was built between 1920-1940. They seem to weather just fine and gradual retrofits to things like electric panels eventually take place. You can’t compare that meaningfully to a mobile home, which is more like a car with a 20 year lifespan. Frankly, I think the building codes are out of control in some respects and add needless cost.

The standard of construction of a middle class home built in 1925 is better the 2022 on the basis of materials alone.