I'm both sides of the fence on this one. Yes, the quality of the jewellery was poo poohed in many quarters - my own High Street independent for one. Because I didn't know any different, I took an overlarge aquamarine white gold ring for him to size down. He took one look at the inside hallmark which was stamped QVC, and he wouldn't touch it. He said that I should return it in exchange for another size, as they "'churned' out their rings in thousands ". At the time I couldn't understand what difference that would make, as he would get paid for doing it. Then I realised it must be to do with the quality.
On the other hand, I still have and wear many other rings, bought during the peak of the jewellery years. The designs were always unique and part of the appeal. Whether or not the pink sapphires/ fire opals/ Russian Diopside/ Peridots/ Amethysts etc etc were of top quality or not, who knows, but they still look as sparkly today as ever they did.
However, I was always more sceptical about the diamonds. There were several varieties - including champagne/cognac/black on offer, but the clear I felt always looked slightly 'dull' with little lustre or glitter, so tended to steer clear of those.