It might not help that in DCs last ten years in of cinema only the Christopher Nolan Batman movies where even comparable in quality to Marvel's(except the Fantastic Four movies). It's possible to do pull it off but very hard to merge the movie 'verses of horrible films into one people will pay to see. They could make a Justice League movie right now or make it after releasing more individual hero's movies with no connection to the universe of each other of the JL movie.
Green Lantern was horrible. Both Superman movies were major let downs, with Man of Steel kinda ruining the righteous good guy who doesn't kill persona Supes had. Even Dark Knight Rises wasn't as well received as its predecessor(high standard there though). Just looking at DC list of recent films this past decade compared to Marvel is extremely slim(9 films counting Catwoman, Watchmen and Jonah Hex; compared to Marvels 12 not counting the 4 Spidermans, 2 Ghostriders, 2 FF4s, 2 Punishers, a Blade and Elektra. So 9 versus 24 cinema releases from 2004 to 2014.)They don't got the ammo to compete with Marvel because the sat and let opportunities slide while rushing poor scripts for major characters like Catwoman and Green Lantern out to be shot(regrettably with a camera not a flamethrower).
They could make a great stand alone Justice movie right now, but they're too scared the general movie audience won't recognize the characters and therefore not risk the $10 on it. I'd say they're either trying to copy Marvel but going slow(See the Batman and Superman with Wonder Woman movie coming soon along with their poor box office history I just typed), someone is trying but another group in the company is blocking it since they think they know how to make good movies(while wondering why people like them Marvel movies so much).
As long as they stop the damn reboots and origin stories, I don't care as long as DC gets their heads out of their collective ass. Have them gloss over the bad movies and build on the character's rich history without destroying the foundation and spending 100 minutes on screen pouring a new one. Wonder Woman can have flash backs occasionally to the time when she was Princess of the Amazons(well she still is but you know). Martian Manhunter can tell the other heroes how he became the last of his kind. Everyone is well aware that Bruce Wayne's parents were shot by a mugger when he was a kid. Man of Steel could have had Supes already stopping runaway trains and catching failing jets before Zod's crew dropped in for a dance with one scene with Jor-El quickly saying "me dad, you alien, planet dead, they bad." Likewise, Sony didn't need to reboot Spidey. All they had to do was throw in a couple flashbacks and a few lines about Peter being bit by a radiated spider while in the Lizard's lab and kick off the plot after Spidey already was in the public eye.