Which led to the huge, gun-less American fighters of the 1960s, the epitome of which was the F-4 Phantom II (https://en.wikipedia.org/wiki/McDonnell_Douglas_F-4_Phantom_...).
Which led to embarrassingly bad kill/loss ratios over Vietnam (see https://en.wikipedia.org/wiki/McDonnell_Douglas_F-4_Phantom_...), when those big, porky fighters went up against smaller, more nimble, gun-still-included Russian planes like the MiG-17 (https://en.wikipedia.org/wiki/Mikoyan-Gurevich_MiG-17).
Which led to guns being hurriedly added back on to the F-4s, first in an external pod mounted on a hardpoint, and then internally on later production models.
Which led to the development of training programs to teach dogfighting skills like the Naval Fighter Weapons School at Miramar (the school immortalized in the 1986 film Top Gun), because it turned out that the conventional wisdom had sunk in so deeply that a whole generation of American fighter pilots didn't know how to fight with a gun, even when they had one.
Which led to the Lightweight Fighter Program (https://en.wikipedia.org/wiki/Lightweight_Fighter_program), an effort to use the lessons learned in Vietnam to design a maneuverable, gun-included dogfighter affordable enough to produce in volume.
Which led to the development of two new fighters, the F-16 Fighting Falcon (https://en.wikipedia.org/wiki/General_Dynamics_F-16_Fighting...) and the F/A-18 Hornet (https://en.wikipedia.org/wiki/McDonnell_Douglas_F/A-18_Horne...), both of which have been hugely successful in service and make up the bulk of the US Air Force and Navy's fighter forces to this day.
But the people who learned those hard lessons over Vietnam are all retired or dead now, so when people say "planes don't dogfight" nobody challenges it.
Which is how the conventional wisdom of the 1950s becomes conventional wisdom all over again.