The "Friends" tab (sometimes "Feed" instead; the A/B testing on this one seems strong) only shows the posts of people you know. Events is still there as well. But in both cases the rate of creation has dropped dramatically since the time you remember, making these nearly useless. That's why the social media services have had to focus on content created by professional content creators instead.
The outcome was inevitable. People had fun posting posts and photos when it was a novelty, but once the novelty wore off they were back to not wanting to put in the effort. You can only post so many photos of your cat before you grow tired of it.
Why would nobody see it? "Friends"/"Feed" is a chronological view of all your friend posts. Unless their friends are posting so much that they can't keep up, which is completely unrealistic these days, your posts are going to pretty hard to miss.
But, in practice, nowadays people who have something to share with those they care about will do so through some sort of messaging application, including Facebook Messenger, so posting really only ends up being for the sake of the casual acquaintances you've accumulated as Facebook friends over the years. What, exactly, do you want to let them know?
Also the way it works, for some reason it decides 2-3 people are my besties (they are not) and just shows me what they post, ignoring what everyone else is posting, so it's still useless.
Who doesn't know it exists? You know it exists. More likely nobody cares to use it because they don't really get much from their acquaintances' cat photos, in much the same way we were unable to come up with anything you want to share with your acquaintances. It turns out that people soon realize that the hundreds of random people they accumulated as "friends" over the years don't actually matter in their life. Those that do matter are already engaged using messaging services (SMS, iMessage, Messenger, etc.). Social media is alive and well, but it moved to places where you can actually be social, away from the "say and spray" venues like Facebook.
Also, you can choose to filter that feed by "Favorites". Did you mistakenly end up in that mode?
The outcome was inevitable. People had fun posting posts and photos when it was a novelty, but once the novelty wore off they were back to not wanting to put in the effort. You can only post so many photos of your cat before you grow tired of it.