In some ways things improved, then regressed, eg
windows became less drafty, but got lower making it harder to see out (standing) and pillars got wider to spoil the view (sitting)
Seats became more fire resistant, but less comfortable
Noisy jointed track went, but sound absorbing soft surfaces also went, anyone remember carpet on lower walls and floors
Gained PA for occasional essential information, much better than waiting for guard to walk down shouting, but then it became automated and excessive
Lighting improved from a tungsten glow, but reading lights went, and then lighting became harsh, especially on commuter trains
Headrests on long distance trains used to have wings, so next passenger never slid or toppled onto you
Armrests lost their padding, (on the Southern and western could put the up and convert 6 seats to 8, lot more comfy than modern tip ups) but nowadays armrests between seats too narrow for both to use simultaneously