First off you have to consider the target for these models. They were were built for kids to be built and played with. They were also used as sales aids for selling full size cars.
By the criterion here on the Corvette many of the Johan kits would be considered junk because of their simplified nature. That is far from the truth. Just look at Steven Guthmiller's fabulous coronet which merged the body with suitable modern production parts. For the most part the older kits have fidelity to the original bodies that isn't always achieved in modern kits.
However there are kits that are junk. Palmer is one infamous case.
Modeling is an experience which varies for everyone. Chose that experience and research the models to fit that expectation. With the internet that information is widely availble.