Let’s take a real look at ISO
Noise is a random fluctuation in an electronic signal, and those fluctuations come from a number of sources.
The fluctuations show up in photos as pixels that are brighter or darker than they should be, and/or are the wrong color.
Noise is present in every electrical signal, and in every photo you take, but the more you amplify a signal, the worse the noise gets.
That increase in the signal to noise ratio makes the random pixel fluctuations a larger proportion of your image, making it look noisy.
This is what photographers are constantly freaking out about.
And this has got to stop.