Never seen an issue where anyone has straight up taken Darkseid down but rather made him retreat to his own dimension. A fight with the New Gods, would kinda put the earth at risk because while they may be able to counter him, he won't lose either. In which case, Darkseid's power is 90% of the time nerfed so that he doesn't wreck the justice league and conquer the earth at his actual power levels.

In all, I think the time travel idea works out better.