It's 339 bytes of CSS which loads 2.3k of font css which loads 21k of woff2. 23k requiring two round trips (three if the stylesheet is in a separate file, four including the initial HTML load), and to prevent FOUT, the browser won't show any text at all until all the round trips are completed (or it decides it's taking too long and shows the wrong font). Plus you're adding a dependency on Google for no good reason.

I mean, it's not exactly worse than other websites, it's maybe honestly worth it because Fira looks pretty good, it's just not really 339 bytes.