Well, the scenario I just described where he takes out 50 people. Or this 532,000 people saved by Flash in .00001 microseconds. That's several trillion times faster than the speed of light. And there was no explanation why he could run that fast, he just always can, so why doesn't he always run that fast. At that speed he could even kill Darkseid by punching him so many times before Darkseid can even react, and the same for every other villain.

But that just doesn't happen. Because inconsistancies where he is that fast one panel and then gets tagged by a non-speedster happen often in comics, and it just wouldn't be a good story to have Flash speedpunch Darkseid so many times that the friction would eventually just remove all the atoms from Darkseid's body and scatter them across the universe, and the same for all other villians. Like what would the rest of the JL do? They couldn't even blink before it was over.

They need to have Flash running at only a few hundred miles per hour when fighting villains so that there can BE a story and not just instantly end the fight.