If you turn off shadows in cs you're putting yourself at a significant disadvantage. Many games have been clinched on a shadow that was noticed.

Not turning off shadows, turning off high quality shadows

Why turn off shadows when you can actually see your own by looking at it? You would be at major disadvantage when playing competitive.

I think you might've misread the parent comment, as far as I can tell they meant turning high quality shadows off, e.g. switching shadow quality to low, not switching shadows off altogether.

Most players prefer the game to look good rather than min-maxing things that won’t affect their score anyway.