It's no secret that the DCEU didn't get off to the best start. While the casting was spot on and the budgets were generous, the film franchise struggled to find its groove with mainstream audiences in the same way as the MCU had. Whether it be a tonal issue or the incompetent meddling of executive suits, the DCEU - as of this writing - hasn't even matched its DC franchise counterpart in the Arrowverse.
The Arrowverse television shows may have small budgets and built around classic CW drama, but what it lacks in cinematic and bombastic presentation, it more than makes up for by wearing its heart on it sleeve. The love and respect that (most) of the characters receive in the Arrowverse have led to its popularity, unabashed to represent its comic book source material for what it is, whether it be beyond cheesy or as dark as the lighting in Game of Thrones.
The steps that the Arrowverse has taken have led the way for both the DCEU and the MCU, whether it be the construction of appropriate tones for the respective character, or pushing the limits for what a mainstream crossover can be.