Warning: SPOILERS for Justice League are ahead!
Although Justice League hasn't faced nearly as much critical backlash as Batman v Superman: Dawn of Justice and Suicide Squad, it's still been met with mixed reception since its release more than a week ago. Some DC fans are under the impression that the latest DCEU entry's reputation would improve if Warner Bros released a Zack Snyder cut that would more accurately reflect the director's vision for the movie. It's extremely unlikely that such a cut will ever surface given that Snyder left Justice League back in March, and with all the changes the movie went through under Joss Whedon's supervision, it's simply not possible produce a fully-formed product that's 100% Zack Snyder's. However, that doesn't mean Warner Bros shouldn't still release a general extended cut of Justice League, as such a version could do wonders for fleshing out the main characters.
Both Batman v Superman: Dawn of Justice and Suicide Squad received extended cuts last year for their home media releases. Suicide Squad's extended cut tacked on approximately 13 minutes of new footage, but aside from a few extra Joker scenes, it ultimately didn't feel too different from the theatrical version, and thus was barely an improvement (some may consider it even worse than the original). Batman v Superman, on the other hand, was a different story. Its Ultimate Edition was 30 minutes longer, bringing the movie's running time to three hours. Admittedly, sitting through that long of a movie can be tough, but thankfully, that extra half hour significantly improved Batman v Superman's plot, so much so that you'd be nuts to ever watch the theatrical version again. Perhaps Justice League could similarly benefit from certain scenes being thrown back in.
It was reportedly mandated by Warner Bros that Justice League be cut down to approximately two hours, so quite a bit of "fat" was left on the cutting room floor, from Arthur Curry's interaction with Vulko to Victor Stone's backstory involving his mother to Barry Allen's scene(s) with Iris West. Justice League did a satisfiable job of fully introducing Aquaman, Flash and Cyborg after they cameoed in Batman v Superman (Suicide Squad, too, in Flash's case), but it still feels like they could have been better fleshed out had the above scenes and possibly other select moments that weren't left out. Even smaller moments like Wonder Woman turning down a swig from Aquaman's flask could just slightly enhance the movie through comedic relief, team bonding, etc. And it doesn't just have to be the heroes who benefit from this. Although most are in agreement that Steppenwolf is a subpar super villain, perhaps there were certain scenes focused on the Apokoliptan general that, when added back in, paint him in a better light.
Obviously not every major shot for Justice League could be thrown back into an extended cut. For example, given how Superman's resurrection played out in the final product, it's doubtful we'll ever see the black-suited Man of Steel outside of non-canon deleted scenes, and I'm skeptical that Warner Bros will even allow those to be released. Obviously it would be great if some of Justice League's bigger rumored moments could be re-incorporated if they still fit into the plot, be it an appearance from Darkseid, Lex Luthor's expanded presence or Batman being visited by two Green Lantern Corps members. But the primary purpose of a Justice League extended cut wouldn't be to deliver more shocks and twists. It's about making us like these characters even more, whether that's by shedding more light on their past or providing further glimpses into their non-superhero lives.
At the time of this writing, Justice League has only made over $485 million worldwide; an underwhelming performance, to be sure. It's doubtful an extended cut being released on Blu-ray, Digital HD, etc would turn its financial woes around. Home video sales are great, but they're no substitute to tickets sold at the theater. But assuming the movie's editors put in the hard work, the longer version would at least improve Justice League's reputation, just like the Ultimate Edition of Batman v Superman: Dawn of Justice managed to do. And hey, if it increases the chances that Justice League 2 will be made, so much the better.