Higher ISO performance of modern cameras is exceptional and that is why I am very comfortable while shooting sports using manual exposure with fixed shutter and aperture and letting ISO float to provide the final piece of the exposure triangle.
In sports, softening/noise is preferable to motion blur but for landscapes you should normally be able to choose a shutter speed low enough to allow closing the aperture enough for needed depth of field while still keeping the ISO low. Modern sensors are definitely far better in low light but there have also been great advances in processing algorithms and it is the combination that has resulted in the incredible low light performance of recent camera bodies.
The below were captured on a horribly illuminated field in the rain and the lighting at that stadium was a "colorful" mix of mercury vapor and high pressure sodium making a bad lighting situation even worse. Captured with a Canon 1DX III and EF 400 f2.8 lens, the first was at ISO 32,000 and the last three at 25,600 with nothing other than standard DPP noise reduction applied during RAW to JPG conversion.
Quite a difference from my first Canon 1 series, a 1D Mark II I bought back in 2005. Top ISO for it was 3200 and ISO 1600 was fairly ugly.
Rodger
