I was an auto mechanic in the 80s. American cars in that period were no worse than they ever were. But they weren’t any better, either, which is why Toyota, Honda, et. al., ran rings around them on quality. As you point out, there was no drop in quality but rather stagnation that looked quite poor in light of a Honda Civic.

To be fair, that ‘81 VW camper in our driveway doesn’t fair much better. I’d rather rely on an ‘80s Chevy Citation to get me home than that piece of parts-bin shit. Part of the problem for a lot manufacturers were 70s-era emissions controls, which is a small part of why a 4000 lb. vehicle has an engine that put out 68bhp.