Turning down graphics in the old days sure was part of the game and wasn't considered cheating. But you also have to consider that the quake era environments weren't as detailed compared to present day FPS standards. Todays shooter games offer much more visual variety with different assets, shaders, texture effects, foliage etc. You try to turn down these things in your GPU's driver settings and you end up with something like this:
Being able to make foliage practically translucent and spot people from ridiculous distances seems a bit unfair to me.
The worst thing is that this can't be picked up by any anti-cheat program, with the exception of PBSS maybe. The screenshots above are just an example, you can do the same in CoD Ghosts, BF4, CS:GO and pretty much any other PC shooter.