I'm pretty sure there are no (commercial) graphite moderated reactors in the US. (Wandering slightly from that point: I'm also reasonably happy to leave policing other countries' nuclear policy to IAEA rather than the US...) So I'm not sure that's a great example.
I'm not clear on what the bargain basement containment is that you refer to. But I have my own understanding of the changes, which I'll share... From what I've heard/read/learned, past light water reactors in the US use used a single containment vessel: steel reinforced concrete, which is also the reactor building. Newer ones have a solid steel containment vessel AND a concrete reactor building (with less steel reinforcement maybe?.
Why this is better/adequate? Steel is much better as a secondary pressure vessel (think Fukushima hydrogen pressure -> explosion). Steel also conducts heat much better than concrete, so you get heat out of the containment without transferring mass out of containment. Then you drip water on the outside of steel containment to remove the decay heat building up inside, and this also controls the pressure, too. The concrete reactor building is your plane shield.
That said, manufacturing that giant steel vessel is an added cost that other reactors didn't have. They also made the actual pressure vessel more expensive to fabricate by getting rid of some of the weld seams. (Said seams end up being the most likely candidate of problems after 40 years of reactor operation, though such failure has not occurred in the US... Fukushima maybe? I don't think we know yet.)
(I am a nuclear engineering grad student, but keep in mind curriculum doesn't spend that much time on actual reactor containment design... so I'm not an expert, per se)