Don't forget vehicles got heavier, rims got bigger/rubber has thinner sides, suspensions geometry evolved and got stiffer (and possibly non-linear, at least on the high end) and so on and so forth, reducing the amount of elastic energy.
There's mechanical braking assistance (not just ABS) which means pressing the same pedal distance may produce different breaking strength depending on the speed at which the pedal is pressed; e.g pressing hard triggers force assistance from, say, a vacuum reservoir that reuses engine pump loss, which means conversely pressing lightly for a normal stop does not need to exert as much pressure, hence an eased in stop.
Also with more stable vehicles with better chassis, suspension, and overall balance, I feel like rear braking has been tuned upwards over time, making for a more stable stop: notice how lightly pulling the handbrake has a straight-rolling car "sitting" instead of "diving". More consistent use of disc brakes instead of drums on the rear end certainly helps, as well as the ability for the vehicle to remain stable even when braking while in a turn.
Regarding brake friction itself, I can think of at least one major change: the ban of materials such as copper or asbestos in brake pads.