A minimalist design approach leaves room for more artistic uses of type. Extremes in sizing, custom typefaces, traditional fonts used in unconventional ways, and highly stylized lettering can all have a huge impact. And with the increased access to typographic choices Google Fonts and Adobe Typekit offer, there’s no need to stick with another ho-hum sans serif anymore.
Combining font sizes can have a huge impact on the look and organization of a page. Single words can take up an entire page. Using vastly different sized fonts creates hierarchy, which in turn supports people in their efforts to understand a website and find the content they want. Larger fonts emphasize the primary messaging of a page, while smaller ones naturally guide one's eyes to the supporting messaging. Designers are making more visually dynamic pages through their creative use of differing font sizes.
It can be overkill to fill a page with flourish-rich fonts, but when used tastefully, this kind of typography can create a strong mood and bring life to a page.