Some of the American chocolate for high volume candy bars is very waxy and not very chocolatey.
For example, compare the Reese's Peanut Butter Cups to Trader Joe's peanut butter cups [0]. It may be that the Reese's ones used to use better chocolate or it may be that my tastes changed as I grew up. But I used to love them as kids and now they taste off. Similarly for Twix etc.
[0] I'm sure other stores sell peanut butter cups too. There's nothing special about the Trader Joe's ones other than they are mass produced and use better chocolate that Reese's.
For example, compare the Reese's Peanut Butter Cups to Trader Joe's peanut butter cups [0]. It may be that the Reese's ones used to use better chocolate or it may be that my tastes changed as I grew up. But I used to love them as kids and now they taste off. Similarly for Twix etc.
[0] I'm sure other stores sell peanut butter cups too. There's nothing special about the Trader Joe's ones other than they are mass produced and use better chocolate that Reese's.
EDIT: Flavor change may be due to cost-saving measures like replacing cocoa butter with vegetable oil https://www.today.com/food/chocoholics-sour-new-hersheys-for...