The Rise and Fall

As the Star Wars Expanded Universe grew, and the E-Wing found itself embedded into its continuity across novels and RPG source materials, textually the ship eventually overcame its initial development hurdles. Generations into its service for the New Republic—it was still in operation nearly four decades after it was first introduced—the E-Wing had seen four major iterations, each one improving on the teething issues of the initial ship, letting the E-Wing flourish as an elite vessel.
But even though the E-Wing was the original face of the New Republic Navy, its initial struggles led to the X-Wing being further developed in its capacity as a multi-role starfighter, and the vessel maintained its position as a primary starfighter for squadrons not at the forefront of the New Republic’s military efforts—save for Rogue Squadron, which almost exclusively remained using the X-Wing as its primary vessel, both due to piloting familiarity and its useful presence symbolically.
Decades after the E-Wing was meant to have replaced the X-Wing with the outbreak of the Yuuzahn Vong War, Incom introduced the XJ variant of the iconic vessel. Although its improved weapons and systems didn’t quite match the E-Wing’s capabilities, the J-Series X-Wing was cheaper to produce, and became the go-to fighter of the New Jedi Order and the Galactic Alliance that went on to replace the New Republic. By the time the Star Wars Expanded Universe was in its twilight, the E-Wing had gone from being the X-Wing’s intended replacement to being kept in its proverbial shadow.