The playbook now is get product-market fit -> own 99% market share -> build, buy, exterminate everything that could threaten this market share -> when the disruption comes, pivot to it.
Zuck inspired the playbook. He's done it to perfection. He's been in the ring for 20 years. Yahoo dominated for about 5-7 years. By no means is he a bad CEO.
Facebook's decline was always a part of his strategy, and whatever the employees say about there being a bazillion active daily users doesn't reflect that their time is near. But Instagram still runs strong and Threads has half a billion active users.