What is musicianship?
"Musicianship" refers to anything that can make you a better musician, above and beyond the technical aspects of playing your instrument that music lessons usually focus on. It includes fundamentals like ear training and theory but also higher level skills like improvisation and arranging.
I hear so many people express disappointment that after years of traditional instruction, they can't play by ear or improvise. On the other side of that coin, many musicians who play impressively by ear tell me they feel limited because they can't read music and don't understand the theory well enough to communicate with other musicians. I also know musicians who have gone to music school and earned degrees but then find they are lost in the professional world when faced with practical challenges like taking a job leading a church group and needing to create simple arrangements.
The things I am talking about here - playing by ear, improvising, reading music, communicating with other musicians in the language of music theory, using that knowledge to create arrangements to suit a particular situation - these are all important to one's success and fulfillment as a musician. And yet, depending on the learning path one takes, most people find they are weaker than they would like in one or more of these or other similar areas.