IDK about the undercarriage, I got rid of a 19 year old wagon that still had its original brake lines. Lots of cars up here need lines at around 8-10 years. They also never have rocker panel problems, a good mix of plastic and good design. The first sign something's amiss is when the subframe rots out. Ironically, it's under the battery, so the acid gets it, but if the car could have just leaked oil on *that side* it would have been free rustproofing.
Volvo is about the only make that I've been under that rusts less.
I'm sure GM had tons of inside politics and accounting gimmicks. Selling saturns at a loss or break-even let them make $15k on every Tahoe and Escalade thanks to CAFE. They could have, and probably did, set Saturn adrift.
The 90s were cool because they only had s-series sedans, so you could option them the way you liked and the engineers paid attention to them. In a way, it was kind of like Hyundai or Subaru, in that a limited lineup meant more luxury "down low". Chevy wouldn't make a Cavalier all that nice because you were supposed to buy a bigger Monte Carlo if you wanted doodads.
The VUE was kinda cool and the platform eventually morphed into the equinox. The ION and van were pretty dopey. The L-series was forgettable. The Euro captured imports (Astra, Aura) were a niche thing but never sold well.
I just bought a couple well worn s-series. There's something about the no-haggle pricing, after all these years, that compels sellers to accept my first, low, offer.