I agree in principle but even something like that is situation dependent. You can absolutely do it a lot of the times, and plenty of songs don't really care what octave a particular note in the scale is in, or whether you play a note open or fretted, or whatever. But sadly plenty do. I was in a rock covers band that did 'Slither' by Velvet Revolver are the main riff, the hook of the song, the bit you absolutely have to get right, is a succession of fretted and then open notes up and down the (low) D string. Now obviously you can transpose that riff easily and play that it any key, you can play it on a normally tuned E string that hasn't been dropped a tone to drop D. But what you can't really do is sit there whilst everybody else in the band is playing that song in D, on drop D guitars, and the singer is singing in D minor, and transpose that riff on a normally tuned bass. Your best bet would be to play it on the high D string and hope that nobody notices there's effectively no bass in that song. Or fret super human fast on the fifth fret of the A and then going back... it'd be a mess.
Sometimes a D tuner or a drop pedal is just the least bad compromise.