I hear youBut that's just it. How low the volume of the other track must go becomes relative to the individual listener.
In my own case, I'd not want to hear the other track at all. That way I can optimally process what is said, rather than nominally process it or lose something in the translation.
Years ago, they used to have several tracks for one video, so they could be more selective and turn the sound way down, including completely sometimes. Now that everything is analogic, for some reason, you get the one track, and that's it. Keeping some of the sound rather than turning it off altogether seems like an editorial choice for the sake of "authenticity", but that's really thinking the viewers are stupid.