Font plays a crucial role in conveying the emotion of a text. Communication becomes effective when a suitable typeface is used. It fails miserably when the font in use has nothing to do with the meaning of the text. Comic or fancy fonts are an example.
Fancy fonts are attractive as the name suggests. Consider script fonts. They are visually pleasing because they make us feel the text is an amazing piece of art, transferred to a sheet using quill and ink. However, the impression fades away once you start reading. Script fonts are really difficult to read for long, especially on a computer screen. Their use makes no sense if the text isn't short and doesn't really scream for a handwritten appearance.
Comic Sans is another example. It's widely used and heavily hated. It was designed by Vincent Connare, taking inspiration from the typeface commonly used in comic books. Microsoft released this font in 1994, and included it in several of their products, leading to widespread adoption. Soon Comic Sans became the default font for many computer users, which was originally intended for funny and informal purposes. Even government officials seem to have used it for serious notices.
Unfortunately, today Comic Sans is so hated that it can't be used even for its real purpose. Here are some websites to know more: comicsanscriminal.com, bancomicsans.com (redirects to linktr.ee/bancomicsans as of Jan 2022), ihatecomicsans.com (domain expired as of Jan 2022).