I am new to B&B, but not new to "real shaving", just returning after a long hiatus....
Yesterday I had my first DE shave in about twenty years, the kit was a nicely preserved 1960s Gillette thin adjustable and Lord Super Stainless blade. The result was a smoother closer shave than I have had in a long time (had been using twin or triple blade cartridge shavers depending on decade) and I didn't go overboard either, just a WTG pass and a partial XTG as cleanup.
This brings me to the "conspiracy theory" part; I gave up on my old DE razor some time in the early 1990s because I felt that the standard Gillette blades in my local drug store/grocery were not giving me a comfortable shave *ever* and were getting dull in only one or two uses. Schick blades (and even some store brands) seemed better, but were getting hard to find reliably and still felt less effective than whatever the current Gillette double blade cartridge system (was that the Sensor?). At the time (and still, looking back on it) I kind of assumed that the companies making DE blades were (to put it kindly) backing off a bit on the quality of the "old style" blades to encourage us to switch over to the more profitable cartridge systems. When this was happening I had no real way to confirm or deny my suspicion since all of my friends were using multi-blade/disposable or electric (shudder...) razors, so years later I am still wondering if anyone else had the same experience?
I know it was a long time ago, but it sure feels like the foreign DE blades are performing like I remembered American blades did back in the 1980s and certainly much better than even a fresh Mach 3 cartridge. Which in a way is confirmation of my suspicion, since the intervening years eliminate the variable of beard toughness (I was in my early 20s at that time, so beard getting thicker/tougher *could* have been a factor), although the shaving cream vs. soap & brush difference is still in the mix (I used to use edge gel, now it's soap and a brush).
I look forward to all of your theories on the past transgressions of the razor blade Illuminati ;)