Not too long ago, I refused to use any ISO over 1600. That was because my old Camera really didn’t perform very well at any number greater than that. But my current Camera is actually quite passable, even up to ISO 12800.
There was a time, when I absolutely loved to shoot in the dark with minimal lighting. I still enjoy doing that. But it also really mushes up the shadows if you Expose for a bright streetlight.
A few days ago, I finally decided to de-limit the Auto-ISO in my Canon M5 from 1600 to 12800. It can go to ISO 25600, but I really don not like its’ performance at that level.
I usually thought that I would get less Noise if I would bring up Exposure in Post. But since the Shadows where usually so extremely underexposed, they turned into pure Black most of the time, or exhibit extreme Colour Noise. I always prefer Luminance Noise over Colour Noise, as it is easier to fix.
So, don not be afraid to use high ISOs. Maybe you will like the results you get. Just get yourself a nice bright lens, preferrably f/2.0 or faster, just because high ISOs are not as bad a thing as I once thought, it is still a good idea to have more light entering your Camera to begin with.