There's actually a company called World Kitchen whose business model is to buy brands with a reputation for high-quality materials and swap them out with cheaper ones:
Pyrex: Used to be made of heat-resistant borosilicate glass, WK bought them and now they are normal cheap soda-lime glass.
CorningWare: Used to be made of a special heat-resistant ceramic.
Corelle: Used to be made of a special break-resistant laminated glass.
You can find people complaining about the massive drops in quality online.