Every designer should have a font that they really love and one that they truly loathe. And they should be able to explain why. For example, I love Helvetica (I know, how cliché right?). But honestly, I really do. I love that it can be sophisticated at a light and narrow or loud in a bold; it’s versatile. And I hate comic sans, again, how unoriginal. But it was meant to be used in speech bubbles in comic strips and as such, I think it could have been an adequate font. But because of its “friendly face” 98% of the time it is used out of context. It is not meant for office memos or school admissions applications (something I experienced firsthand just last week).
Learning why you love or hate a font will make you a more attentive designer. You will come to see the subtle nuances of the fonts you use.
Knowing fonts intimately enough to have one to love and one to hate shows that you care about design.
Caring enough to be passionate about fonts will make you a great designer.