Being a good musician and a professional musician are mutually exclusive terms in many examples.

Anyone here can like play circles areound Paul Mc Cartney or Ray Charles on the keyboards and not be considered great musicians. (Probably because tey have not achieved the professional LEVEL of the latter which somehow crowns them witnh great musician status...)

On the other hand someone who plays like Nicholas Angelic and has not achieved the professional level ma be considered a lesser musician.

Arrangers shine for songwriters who do not want to play the parts in the arrangement of heir music because those who can and do are better suited to it. Those of us who had workstations or years had to play all the parts and arrange all the orchestrations which although was fun was time consuming and less than it could be.

A workstation is a hand held hammer. An Arranger is a powered hammer. They both serve to build a house equally as strong. However the carpenter with the single hammer will take longer to build the same house.