Where the Star Wars universe differs from WW2 is in its mature starship technology. Aircraft such as the A-10, the B-52, the F-15, and the MiG-21 have taught us that as long as a technology is useful, it will stick around.
The Y-Wing was designed and developed by Koensayr Manufacturing in the tense years before the Clone Wars. Aimed at smaller planetary markets, the vehicle was designed as an escort fighter, cheap to fly and cheap to maintain. The eventual production model proved overweight and underpowered. According to those early pilots, "it put the dog in dogfighter."
The Y-Wing would have gone down in history as a market failure if not for the Clone Wars. The sudden outbreak of war demanded fighters immediately, while procuring additional fighters required that manufacturing build more factories. In the face of this crisis, ground crews modified the existing Y-Wing fighters by removing weight and overcalibrated their engines. With those field changes, the humble Y-Wing's fortunes turned, quickly proving itself the best cheap starfighter in the galaxy.
The Y-Wing's saga didn't end there. Because these fighters were so easily modified, planets were able to retask these fighters into numerous roles, such as scouts, ground attack fighters, minesweepers, couriers, and torpedo boats. By the war's end, these fighters had become the predominant starfighter in the Outer Rim. General Dodona said, "They did everything that we asked of them and more."
With the rise of the Empire, the need for region defensive craft diminished. Planets that voluntarily accepted Imperial Garrisons were required to scrap their local fighter groups, and so the Y-Wing quickly disappeared from arsenals and resale lots.
With the rise of the Rebellion, salvaging those Y-Wing became mission #1. Their ease of repair and modification was exactly what the Rebellion needed. Aggressively recruiting veteran Y-Wing ground crews, General Dodona pushed the vehicle far beyond its original specifications, producing a strike fighter capable of matching matching the new Imperial TIEs. The resulting craft proved so capable and resilient that they led the Rebellion's attack on the Death Star. Late in the war, as better and more maneuverable craft arrived, the Y-Wing continued proving its worth, maintaining its place in the Rebel arsenal through the dogged innovations of its ground crews.
After the war, Y-Wing pilots often boasted, "The X-Wings got all the glory, but the Y-Wings did all the work."