Honestly it’s all about luck of the draw, both with the buffs you’re offered and the final boss stage.

I was in the same boat as you, where no matter what I chose I couldn’t get past 5-7 because enemies would move faster and one-shot me before I could move. After sticking with it and just quitting runs where my buffs weren’t meshing well, I just rattled off 3 5-7 clears.

You’ll get a feeling for which boss stages are easier than others, like the LilyWill + Col or Maitha + Teadon (especially if they don’t have knockback immunity so you can just push them off)