People would know that chocolate didn't taste as good to them as it used to, but how many would think that the fault was with them? Many might think they'd just outgrown chocolate, or that nostalgia misled them into thinking it used to be better than it is now. If just one product got worse, that would be one thing; but if the whole category of cheap chocolate becomes lower-quality stuff, people may be more likely to think that they're the ones who have changed.