B&R probably made WB finally get serious about a Batman movie, as a change. It was such a fail that WB really had no other direction to go. And in that sense B&R definitely paved the way for Nolan to get that shot and for a movie trilogy that truly earns the name "Dark Knight Trilogy." But I do wonder if the involvement of Liam Neeson, Gary Oldman and Christian Bale might not have been due to Stewart and McKellan being involved in X-Men. Probably its a number of factors like that all coming together, with B&R firmly in the background looming there as if saying "do anything but this!"
As much as B&R is reviled, it has more in common with the MCU films than with the DCU films. Aquaman and Shazam are really the first WB hero films to feature any humor since B&R