Not sure I follow the "we are looking at two possibilities here". There's an equally plausible third possibility - Zuckerberg's claims to have engineered the reduced time spent on Facebook could simply be a ploy to save face as his platform loses relevance. In fact, that's textbook corporate behavior. Usage has been slipping for some time now, ever since the toxicity which exploded during the last election. Shareholders want answers and reassurances their golden calf isn't ailing. My guess is Zuckerberg will slowly be devoured by the same capitalistic Darwinism which created him.

Personally, I think exiting isn't a bad idea. As we all know, you aren't going to change people's minds by arguing with them in Facebook feeds and with the signal to noise ratio in any given social media platform, most attempts at some change from within can be easily ignored. Unless you want to pull a Putin and use the system's data hoarding against it. That's actually kind of genius (and, as we've seen, will do more to damage Facebook than some lone poster spamming people's feeds about revolution and what not.)