Most significant advance in bike technology for speed?

In another forum, someone postulated that integrated brake & shift levers (like STI) were the most significant bit of racing technology ever designed for increasing speed. But that claim met with little respect. One skeptic noted that there was no great increase in average race speeds in Paris-Roubaix, Milan-San Remo, Tour of Flanders, Leige-Bastogne-Leige or Giro de Lobardia since about 1960, including during the era of STI adoption. By contrast, in the  years 1930 - 1960 average speeds increased around 30%. (Note: That does not mean that STI is not tactically beneficial. That's a separate issue.)
But if not STI, what were the most significant tech developments regarding bicycle race speeds?
Here’s my list:
Pedals & cranks, as opposed to scooting a “hobby horse” via feet on the ground.
Tubular metal frames and wire tension (spoke) wheels.
Large driven wheels, to give a much higher effective “gear.” (The Ordinary or Penny Farthing)
The “Safety Bicycle” with a diamond frame and chain drive, getting the rider down lower, to greatly reduce aero drag as well as pitchover on braking.
Pneumatic tires. Hard tired “safeties” had terrible rolling resistance.
The handlebar stem, invented by the heroic Major Taylor, to allow a much more aero riding position.
Rim brakes, by whatever mechanism, as opposed to spoon brakes acting on a tire.
Multiple gears, by whatever mechanism.
The derailleur, making multiple gears easy to shift, customizable and light weight.
Recumbent geometry in some situations. Recumbents seem to be slower uphill, but tend to be faster on level or downhills
Fully enclosed streamlined aero shells tremendously increased speed, but at a great reduction in versatility and practicality.
Beyond those, ISTM that most developments have been chasing ever diminishing returns.
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- Frank Krygowski