Sandberg may be a "professional grown up adult", but that doesn't preclude her from being a liability to the company.
As one example, because Sandberg was at least partially responsible for blocking attempts at reforming data policies inside of Facebook that likely made the Russia tampering mess worse. And then Facebook corporate attempted to cover that up by pushing the NY Times to alter its reporting:
https://lawandcrime.com/exclusive/facebook-forces-nyt-to-qui...
Further, Sandberg was the core architect behind Facebook's ad business and shift to aggressive monetization. She was brought in from Google precisely for that reason, that's why Facebook recruited her from there.
[2008] "Ms. Sandberg, currently vice president for global online sales and operations at Google, joined the search giant in 2001 and helped develop its immensely lucrative online advertising programs, AdWords and AdSense."
"She will also oversee Facebook’s marketing, human resources and privacy departments — essentially guiding how Facebook presents itself and its intentions to the outside world."
[1] https://www.nytimes.com/2008/03/04/technology/04cnd-facebook...
Zuckerberg compared to other CEO level executives have a fairly good track record. Somehow his mistakes were not an issue for you for last 10 years and now you have a tough stance against him. What you are buying into now is a form of propaganda where it is fashionable to bash him.