Avec les courbes pouvoir agir que sur la luminosité et pas en RGB comme chez vos concurrents

It seems that the Luminance function in in DxO curves has no equivalent in ACR.
A workaround would be to reduce the saturation after applying a curve in ACR.
You can use the the Color mixer to adjust the saturation of individual colors.

 

Yes, manipulating these tone curves in ACR can affect saturation.
 

Yes L is for Luminance. Does what you're describing in ACR not alter the colors, and therefore have no indirect impact on color “saturation”?
 

I don’t use DXO, so I’m not sure what the L function does.
Luminance? If so, it does the same thing as in the two screenshots I posted from Camera Raw.

With the curves, choose to adjust only the brightness and not the RGB as with all your competitors.

If I understand you correctly, you want to adjust the brightness of the whole image, not individual RGB channels.
There are two ways you can do this in the Curve panel.