I use WhatsApp for family chat so we noticed early. If you're not really invested in the FB ecosystem (FB, Instagram, WhatsApp) and don't use other social media (Twitter, Reddit) it'd be hard to notice.
When FB bought WhatsApp I was pissed, because I knew what it meant, and this is one of the consequences of monopolistic conglomeration. Instagram to a lesser extent, though I use that far more than FB now. FB is for old people and suburban/rural moms in MLMs. And vaccine research, of course.
I find FB interesting as a business. Most young people hate it, it's growth is largely concentrated overseas, and its growth in its demographic targets is mostly due to Instagram or other acquisitions. It's pretty poorly positioned for the future, as it's a destination rather than a portal like Google. But it's also huge and entire businesses architect themselves around its ad model and network graph. So how can you leave? I expect it to get more aggressive/illegal in its hunger for youth data. Better to take it however they can and pay whatever fines rain down from weak governments as those fines won't even touch the value of the data. Just a cost of hegemony.