In another interview, James Gunn shattered spirits by confirming he isn't trying to replicate the MCU. Apparently, Darkseid is not going to be the ultimate big bad of the MCU after all. Actually, Gunn doesn't think that the franchise needs an ultimate big bad, but I think he is wrong. One of the reasons why the MCU's infinity saga did so well is because everyone knew that every character, and scene across all the films and TV shows were in service of the one ultimate purpose of defeating Thanos.
I do understand the continuity nigtmare that comes with having a single big bad, but it also serves more benefits. If the DCU is to continue as a single unit, it has to have a common enemy for all the heroes to unite around. It doesn't have to be Darkseid but someone needs to be.