While WeChat was adding features, such as an independent creator marketplace, or payment systems, Facebook spent time aggressively pushing online web games that almost killed their platform.
Then Facebook started going for attention metrics above all else, and it became an app that fed people stories that made everyone angry and depressed, but did a good job increasing engagement!
Facebook should have started cloning WeChat features years earlier than they did.
Facebook's other problem is their real name policy. Having to be friends with someone to message them seriously limits how many people I talk to through Messenger.
But as it is, Facebook Marketplace is winning. Facebook events is winning. Facebook payments, no, not sure how they messed that up. Venmo and a few others are duking that one out, heck Venmo is used at garage sales.
Facebook doesn't need hyper growth, they need to just keep current user's happy and coming back for things. It doesn't matter if they aren't the #1 destination for GenZ to post photos. If everyone is buying/selling used goods, and going to concerts, and arranging birthday parties, and posting a small selection of curated travel photos, then be happy with that, and keep expanding into adjacent markets.
And separate out "people I want to talk to" from "people I want to show my life to".