I have plenty of people in my extended friend group who are in their mid to late 20s, and most of them are still quite active on FB.
Nobody thinks it's cool or fun anymore, of course. But it's still the go-to spot for sharing life events, family news, anything you want to brag about really. Or any vacation pictures that you'd like grandma and grandpa to see.
IG is still image driven, so it's not a platform you can easily use for relaying text based information to your social network.