Unless you are at an elite institution in a highly specialized department that has no general education or service course teaching responsibilities, you need generalist faculty. Most academic departments at non-elite universities have to cover an increasingly wide range of courses—especially at the undergraduate level—with a small number of faculty.
Although we get our doctorates in specialized research areas, most of us—if we are lucky enough to get a full-time faculty position—need to teach much more than our specialized research focus. Someone whose scholarship focuses on Shakespeare, for instance, may work in a small department in which they need to teach surveys courses on English literature to 1800, Chaucer, poetry, the English novel, intro to literary theory, the history of the English language, and the occasional American literature course—not to mention first-year composition and advanced writing courses. Probably they have a four-course per semester load as well. This combination of demands can lead to exhaustion, complacency, and dissatisfaction of all kinds.