In any case, business perspective prevailed, subject matter experts stopped sticking around. Personally, I think the (slow but steady over many years) switch from b) to c) is what doomed the site.

There was a few noteworthy company post, especially those after the mass layoffs / private equity takeover on the meta site that acknowledged the problem, so its certainly not a), even when you apply a strict standard about the terms in which to acknowledge the problem (which was well-known long before). Those company statements had some rather clear and well-received community commentary below that essentially questioned whether any of the suggestions on tackling the problem should even be tried. The very-much-not-welcoming onboarding experience, while it had great potential for improvements, was yet serving the sites unique needs quite well. Two weeks of persistence and reading the manual were not much of a detrimental filter.. not to those that would eventually go on to contribute back for many years. And those were the ones that ultimately mattered. Not those one-off solve-my-homework posts that only saw indifferent/annoyed moderation action. That probably still wonder why nobody took their hand and spent their evening guiding them through the steps necessary to make their post useful to anyone other than just the original author.