I think the problem with a high iso capable camera is that people use the high iso in lieu of lighting correcting.... exposing correctly. I'm occasionally guilty of this myself
Jd....I think I understand what you're saying....
I have shot at poor light sporting events where the action is stopped, and I continue to shoot manual at 1/1000 and ISO 3200, even though the subjects are moving slow or not moving much....they are exposed correctly, but the image quality would be better if I quickly switched to 1/500 and ISO 1600....or maybe 1/250 and ISO 800
I probably should use my custom settings more to do this.