I prefer the idea that it's some kind of parody universe where similar events happen. The timeline is actually completely different at certain points, like the first invasion force being lead by Steppenwolf rather than Darkseid, so it's not like they diverged at a certain point. Tonally, it works better as a standalone movie.
Though, I do understand that the original intent was for it to be a sequel to Batman v Superman: Dawn of Justice. At the same time, though, the intent was also for it to be canon to the DC Extended Universe.
If David Ayer's Suicide Squad gets announced, for the sake of consistency, I would say that including Man of Steel, Batman v Superman: Dawn of Justice, Suicide Squad: Extended Cut and Wonder Woman in the Josstice League universe makes sense.
Say that they're extremely similar universes but fundamentally different at points.