I’ve been using Mach 3 carts since they first came out. I can’t say that I’ve noticed a difference from then to today. What has struck me recently is that every so often a pack of carts seems milder than what I’m used to. Perhaps, however, this is due to my paying closer attention to the feel of a cart on my face than I have before.
Gillette blade quality has only improved through the years as a mere glance at their patents shows. They pump a boatload of money into R&D. Do you really think the Koreans (Dorco) or Harry's (debt financed to the teeth until sold recently) do that? No way, José.