A low quality noisy image is not properly exposed, hence does not follow a Standard.
In the film days, ASA is about the sensitivity of the film. It is a standard that says at a certain amount of light, this film will react and produce image.
Today's ISO is not about sensitivity of the sensor, but rather the amount of amplification the camera does to the sensor's signal before it saves the data. That is where the problem happens because theoretically, we can up the ISO to any amount. The issue here is the signal to noise ratio. Granted that we may want to opt for getting the image whatever the cost, there is an optimum level and that is what it should be stated as a standard.

My point is that to comply with a standard, cameras should state the highest ISO number where an image is clean as their Actual working ISO. Any ISO beyond that should be called extended ISO limit.

The price of high ISO is noise.

Random noise represnets the loss of information from the image file.
Maybe you don't care about information, but you probably care about money.

At ISO 100, your $1800 lens looks like $1800.
At IS0 200, it looks like a $900 lens
At ISO 400, it looks like a $450 lens.
At ISO 800, it looks like a $225 lens.
At ISO 1600, it looks like a $112.50 lens.
At ISO 3200, the photo look like it was taken with a $56.25 lens...
with fingerprints on it.

The choice is yours.

There are alternatives: faster lens (e.g, a prime), good off-camera flash,
lights, or just wait for better light.

There is a way to have high ISO without noise, used in space telescopes:
cryo-cool the sensor. Short of that, there is no way to turn up the sensitivity
without getting more "static". There is always thermal (Johnson-Nyquist)
noise.

Since solid backgrounds are more common than speckled ones, clever processing
can hide th enoise by filling in tiny white spots in a dark backgroun. But is the
background really had tiny white spots, you lose. Or if there are tiny black
spots in a white background--since these are very common in real scenes.

The trouble with random noise is...it's random. It destroys information.
had tiny white speckles,

I think we all know from previous discussions that ISO performance varies considerably from camera to camera. I have to wonder if a sensitivity of 800 ISO on one camera is even the same level of sensitivity on another camera set to 800 ISO? If this varies considerably, they can call it anything they want, we are not comparing apples to apples. So, is noise really the only variable factor between two cameras set at the same ISO number? In other words are the ISO settings equal from camera to camera where we should get very similar exposure performance at the same ISO level or does this also vary from camera to camera to compound the problem of making direct comparisons?