You are absolutely right of course chas ! But you could say the same about any instrument that any arranger or keyboard is trying to emulate . A top professional could get sounds out of a simple triangle that a keyboard cannot ! Let alone an almost living breathing beast such as a Hammond organ .

An arranger can at best mimick most of the character of an instrument for a skilled musician to attempt to play well and in almost every category of sound it does it well . But perfectly ??? No not a chance .

Can an arranger fully replace any original instrument ? No not a chance ! But can it cover most of the bases to enable a skilled musician to fool most listeners that they are hearing the real thing ? Certainly it can !

I don't have the time to master the emulation of every instrument I love . But I can play guitar reasonably well and the keyboard/piano and the drums so I ha e an appreciation of what I should hear when playing or singing with a live band . The arranger does an "adequate" job for me when I don't have real players around me . It's not a substitute but it is sufficient for what I need it to do .

What I do is arrange . That's what an arranger does best .