There are many facets to quality. I'm not 100% convinced that "Made in Korea" Lionels were better. Just a few of the examples that burned me through the years: Odyssey "lurch," exploding Odyssey flywheel magnets, nylon gears in the Niagara, EM-1 driveshafts, Hudson wheels held to their axles by tiny screws that strip out easily. Wheels on the loco that didn't match the pre-production catalog image. A veranda turbine with bent subframes. "Scale" diesels that rode much higher than a postwar 2023 or 2343. TMCC circuitry that worked poorly in conventional mode; sound and command board configurations that were failure-prone and difficult to troubleshoot (and would probably necessitate an ERR upgrade to perform as well as the best of today.)
I'm not necessarily a fan of China or toys that are made there. And I agree that the quality of some recent pieces, especially those made in 2017-18 (such as the Moguls, F40PH, etc.) was very questionable. Not to mention inaccurate paint colors! But- there were many engineering improvements that came with the introduction of Legacy and shortly after.
During the 2001-2007 time frame, in my opinion MTH (the original "Made in Korea") ruled the roost. When Mike lost the lawsuit about the N&W Class A, etc., I recall him being quoted as saying something like "now that this has happened, within 7 years Lionel will catch up." If he really said that, he was almost exactly right! After 2007, Lionel's engineering improvements, i.e., back-drivable gears, Legacy, the CAB-2, dedicated controls for a quillable whistle, etc., offered more to the operator than MTH. Beginning with the FEF, Milwaukee S3, etc., Lionel hit one home run after another. MTH retreated to HO steam (which ironically incorporated the improvements I had been requesting for years!), and European trains. Lionel got the majority of my train dollars for the next 7 years.
Like some of you I spent a LOT of money on trains during this time period. My experiences were real. My interpretation of the facts is subjective, but being heavliy into the hobby during this era, that's how I perceived it.