Why the Change?
Older mattresses were thinner and built with interconnected coils that needed a shock-absorbing box spring to prevent wear.
Modern mattresses are heavier, thicker, and made with foam or individually wrapped coils. They need a rigid, non-flexing surface to support their weight and yours. Putting a heavy memory foam mattress on a bouncy box spring causes it to sag in the middle, creating a "hammock" effect that ruins support and voids the warranty.
"But I have a bed frame that requires a box spring for height..."
Instead of a traditional box spring, buy a "Foundation". It looks exactly like a box spring (fabric covered wood box), but it has solid wooden slats inside instead of bouncy springs. It gives you the height you need with the rigid support your mattress requires.