Bingo.
Part of the whole origin story of TheFacebook that falls in line with this is that his university actually had a print version of a compilation of people's face - I presume like a yearbook - that they were planning to make an online version of; it was actually called The Facebook from my recollection, and another place Mark wasn't creative or innovative and took from as well.
Apparently they were taking a long time to make the site, Mark couldn't understand why. The reason? Apparently the group who was working on bringing the print version online were brainstorming through the potential consequences of doing so.
I remember reading about it many years ago online in one of the university's student newspapers, I think I remembered it correctly but my memory of it is a little fuzzy; I believe it'll be in one of these articles: https://news.harvard.edu/gazette/tag/mark-zuckerberg/
I don't think the problem at Facebook/Meta is that it's a mortal sin to reduce engagement, I honestly think they just aren't creative enough and they don't understand from foundational principles why they have what they have, nor how to improve on it in a nuanced way.
As you said it's basically an industrial machine with very few wheels, where all of the basic or crude parts are in place, where their guide is the most basic-shallow metric possible is whether engagement goes up or down; where it's the network effects that kept it together for so long. Mark certainly isn't a creative visionary, and so with him at the helm, all of his decisions of who he empowers under him will be random as to whether they are beneficial or not - but logical decisions looking at user numbers and growth made purchases like WhatsApp and IG no brainers.
Interestingly, you are actually correct, in that the original meaning for sin is aim related - and so because of their lack of sophistication, the only thing they see or know how to aim at are engagement numbers. The sin will be by not aiming at the only thing they are good at aiming at, where they otherwise miss the mark - and sin; is it irony that his name is Mark and he's arguably been missing the mark this whole time - or perhaps a generous perspective is that he's really good at hitting one specific mark, the Mark? Anyway..
In contrast, Elon Musk functions creatively, an imaginative open mind, and has developed an understanding of first/foundational principles that he works from. Twitter will likely be a good buy once Elon re-lists it. I'll still be investing in my projects though.
I have been working on my own platform solution to solve for our society in crisis mode. It unexpectedly was a relief when Elon bought Twitter, as I am primarily driven by necessity. Elon will course correct Twitter away from the ideological and censorship bent platform it was becoming, so at least there's one major battleship on our side, funded by the person who most definitely has Fuck You money and competent to boot.