I prefer to call myself a quilter, since 98% of what I do at a sewing machine is quilt.
I think of a tailor as a man who sews and alters apparel, while a seamstress is a woman who sews and alters apparel.
I don’t care for “sewer” but am warming to the term, as “seamstress” sounds outdated, much like “actress”; today’s female film stars wish to be called actors.
Sewist? That just sounds corny to me.