The DCEU wasted a major DC villain, but the DCU's upcoming Teen Titans movie can do the character justice. Several characters were set up to become big players throughout the DCEU's 15 movies, but some of them didn't get the opportunity to show their full potential before the DCEU concluded. For instance, the Joker only appeared in Suicide Squad and Zack Snyder's Justice League, missing the chance to become a recurring DCEU villain. Similarly, both cuts of Justice League teased the team's imminent battle against Darkseid, but the franchise ended before they could cross paths.

https://screenrant.com/teen-titans-dcu-movie-deathstroke-future-fix-explained/