I really think that something changed with a major potentiometer manufacturer in the past few years.

I've heard a lot of hearsay that that is the case. Tech savvy people have taken apart some sticks and say that analog stick quality has taken a nosedive in recent years. Maybe it is just the effect of this sort of thing being discussed on the Internet more often, but I don't doubt the veracity. I've had a few older controllers that I retired because of external wear whose internals were totally fine. Seems like controllers like Dualsense and particularly Switch Joycons are just poorly made.