While this article might be old as fuck, it's still relevant IMO.

Morally speaking I'd say that it is a duty, but a weak one, since it depends on:

1. how responsible the person can be held for condoning what the platform does, based on what the person is attested to know about its role on political and social manipulation. Or, you know, genocides.
2. how much undue social/professional harm the person would cause themself, by leaving the platform. Because people there aren't just partners, but also victims of that platform.
3. their direct role on Facebook's misdeeds. Someone who passively checks the news there is simply not on the same level as, for example, people spreading misinformation.