It's actually simple. All the old shows like The Flash or Supergirl were killed by another show called Daredevil.
I can't go back and watch some cringy badly written teenager show with no continuous plot. I mean it with no offense to DC's Arrowverse but nowadays I prefer a series with a short season of interconnected episodes than 24 episodes with 10 useless in the middle.
So yeah Crisis is happening but it should have happen in the big screen at the same time as the peak of the MCU with end game.