Google Fonts is always a bottleneck for website performance. The Google Fonts' CSS is a render-blocking resource, which means that the browser won't render any processed content until the CSS is loaded. It also causes a blank space when the font is being loaded.
Nowadays, except system fonts, Google Fonts is the optimal option of most websites for typography. However, there will be 2 disadvantages when you load Google Fonts for typical websites as instructed by Google's tutorials, or by the way to enqueue CSS in most WordPress themes: