A modern pit stop is completed faster than most people can react to a traffic light. Achieving that is a problem of sequencing and signalling rather than of individual speed.
The tasks are parallel, not sequential
Each corner of the car has a dedicated group: one operating the gun, one removing the old wheel, one fitting the new one.
All four corners work simultaneously, while separate crew members raise the front and rear of the car and others stand ready for adjustments or damage.
Nothing waits for anything else, so the total time is set by the slowest corner rather than by the sum of the work.
Every position is fixed before the car arrives
Crew members are in place with the new wheels held at the height they will be fitted, so no movement is spent reaching or turning.
The stopping position is marked precisely, because a car half a metre out of position forces the crew to adjust and adds more time than the error appears to justify.
This is why a driver overshooting his box is costly out of proportion to the distance involved.
The release is automated because humans are too slow
Each wheel gun signals when its nut is torqued correctly, and those signals feed a system that indicates readiness rather than relying on someone judging it.
A person watching four corners and then deciding would add several tenths, which is a large share of the total stop.
The final release still requires a human confirmation that the pit lane is clear, since the system knows about the car but not about traffic.
Failures are usually cross-threading, not slowness
The most common problem is a wheel nut that does not engage cleanly, which forces a retry and multiplies the stop time.
Because the crew is committed to the sequence, recovering from that error is awkward, and the surrounding crew members cannot help without creating a second fault.
Teams therefore practise the recovery specifically, rehearsing what each person does when one corner fails rather than only rehearsing successful stops.
Why the times stopped improving
Regulations introduced minimum intervals between certain stages of the stop, deliberately preventing the release system from operating at the speed it could.
The purpose was safety, since a car released with a loose wheel is dangerous in a way that a slightly slower stop is not.
Stop times consequently plateaued, and competitive advantage moved towards consistency, with the strongest teams distinguished by how rarely they have a bad one.