Is Facebook’s Importance Decreasing

In short, yes.  Most folks use Google searches to find your website. [2]

If not Facebook, what?

As of June 2018, it looks like YouTube, Instagram and Snapchat are tops on the list.  Facebook is no longer the social media of choice for teenagers and young adults. [1]

Do I give up on Facebook?

No, but your strategy must change.  Check out these tips for Yoast.

References:

1. Pew Research Center, May 31, 2018 – Teens, Social Media & Technology 2018 – YouTube, Instagram and Snapchat are the most popular online platforms among teens. Fully 95% of teens have access to a smartphone, and 45% say they are online ‘almost constantly’
2. Chartbeat, Terri Walter and Su Hang – Mobile Direct Traffic Eclipses Facebook