The world's biggest social network isn't getting any bigger.

Meta posted its fourth-quarter earnings Wednesday, sharing financials that disappointed Wall Street enough to send the company's stock into a nose dive. Shares of the company, still trading under the ticker symbol FB for now, plunged 20% as the numbers hit.

While Meta's final quarter of the year has been a doozy, with trends expected to have played out-on one hand, for example, Apple's iOS change on privacy dampening its ad business-it has also called into question the novelty of an entirely new fact: Facebook, Meta's flagship app, is no longer adding new users.

Actually, Facebook's MAUs held steady from the third quarter of 2021 to the fourth at 2.9 billion. Worse, its DAUs fell from 1.93 to 1.929 billion in the same period. That marked a first for Facebook, known for its growth-at-all-costs approach.

Some of this is intuitive. Facebook is a mature product (to put it gently) and there are only so many humans in markets around the world left for the company to sign up. And the company is placing more emphasis than ever on its "family" of apps, including WhatsApp and Instagram, fresher products that likely still have a ways to go to reach that kind of saturation.

The slowing pace in user growth came in the same quarter when the company now formerly known as Facebook revealed its plans to rename the organization as a "metaverse" company, together with plans to steer its resources toward building immersive virtual experiences.

Good news for Meta: it still owns the world's biggest social graph. Bad news? Even when a user slowdown was likely inevitable, it's just one more thing making Facebook — and hence Facebook's "Family of Apps," as Meta calls it — look more and more like a relic from the past rather than a shining vision of the future.