Yes, Justice League is by far the worst DCEU movie, and the reason why is a bit more complicated than you would think. In philosophy is this: every single DCEU movie prior to this one at least tries. Despite how bad and incompetent they are, they still had potential, mostly with MoS. BvS sucks but despite all the forced Comic Book trope, there is/was clearly a lot of love and care for these characters, or else they wouldn't bother to include all the references, badass fight scene, Batman's DKR armor and so on. They are bad but they try to be good.
Justice League doesn't try to be anything but the most forced Comic Book live action adaptation ever, and it does not know whether it wants to be a sequel to MoS and BvS or try to apologize for all the bad things in previous movies by pretending they never happened and giving us a different lore and characteristics of already established characters.
For example, in BvS, Batman was similar to his Dark Knights Returns self. Older, broken and tired man who's dark, aggressive and brands and even kills criminals. In this movie, he watched his lake from his mansion, desperate without the beacon of hope that is now dead Superman. Oh yeah, Superman. Superman went from depressed, hopeless, reckless maniac to more optimistic and hopeful self (with CGI lips, Jesus...). And that's great. But the problem is, THAT'S NOT SUPERMAN THEY GAVE US! I get they want to fix their mistake but this change comes from nowhere. They just want to force this Superman in and hope it makes it good. It does not, and the fact that this world suffers so much due to lack of hope that was Superman is just astonishing. Who wrote this movie? Superman was NEVER a beacon of hope in DCEU. He was reckless idiot and EVERYBODY HATED HIM. That was the whole point of BvS and that is how Batman got introduced in this Universe. The continuity between MoS/BvS and this movie add up less than Fox's X-Men movies.
Besides that, everything else is just a mess. Boring villain, bunch of fodders, forgettable Aquaman and Cyborg, and the only good thing in this Universe (Wonder Woman) barely being used.
The worst part of this movie for me is the Flash, and I don't think I have to tell you why. Any person who ever picked up a Flash comic would know that whoever Ezra Miller plays is not Barry Allen. Hell, not even Wally West and Bart Allen act like this. Apparently Snyder and Warner Bros think Barry Allen is some weird combination of black Wally West, Miles Morales and Peter Parker from Ultimate Spider-man cartoon.