That's a fair thing to be concerned about - any blind faith is a problem. We should always be ready to, if not slaughter our sacred cows, at least take them to the vet once in a while (apologies for the tortured metaphor).
That's depression, not nihilism. Nihilism is related to existentialism, and is about believing in nothing but what you experience or can prove. Unfortunately it's very close to some forms of scientism, whereby someone makes "Science" their religious faith. The idea of nihilism is to be faithless and to view the world through the lens of the material.
Greek yogurt? Yuck. I could see it with just whipped/beaten cream cheese (since the best cheesecake is basically whipped cream cheese, lemon juice, and sugar), over some kind of biscuits (since I happen to like a graham cracker crust)
I mean, yes. But I was trying to get at why it works and what would be needed to change the status quo. Tbh if Facebook or Twitter could be prosecuted for their role in harm to children or sex trafficking, schools would very quickly be ready for change.
I get your frustration. Why don't they care? Have you asked people directly what benefits they get from Facebook and why they won't move?
I expect you'll get the following, based on my experience:
Exposure - Most people can access Facebook regularly.
External Accessibility - Facebook can be accessed on multiple devices, by people who are not tech-conscious.
Reliability - Facebook outages are rare enough to be newsworthy, so no matter what conditions the school or the org is in, it will stay up and be exposed and accessible.
Internal Accessibility - Everyone in the org, even the people who aren't regularly involved in marketing or community comms, knows how to post to Facebook.
Cost - Facebook's non-monetary costs are subtle and mostly apply to private users. To any organization with a tight budget, Facebook and Twitter are godsends, because they don't need to have a P&L line that can be scrutinized and audited. I'm sure you understand as a volunteer how important it can be to dodge the accountants while getting messaging out.
Of course there's also experience, knowledge, and negative inertia built up over time. Until you can cover all 5 of those points at least, you don't have a viable option. Nextcloud is neat, but who will administer it without pay? Facebook runs the platform without being visibly paid by the school or the org. Facebook has widgets prebuilt to integrate with the website (that the org also outsources administration of). Nextcloud doesn't natively have that. Facebook is hosted on a massive network of data centers, Nextcloud would have to be run on one mistakenly undiscarded computer acting as a server in the basement. And it would have to be that way because the org doesn't have the budget approval for AWS or added hosting. And yes, everything will always come back to that cost issue. Until you can beat that, you have nothing.
Anger is pointless without action. Either accept the situation as it is, or start regularly attending school board meetings. If you want a policy changed, speak out about it. Don't just give them vibes either, give them good reasons to change the rules and processes. Have a solution at the ready which is idiot-proof, accessible, and well-supported. Oh, and also, make sure that your clear solution is zero-cost, which is why schools fell into using Facebook and municipal groups used Twitter.
If you want to change the situation, you have to understand why it became the way it is and address the pain points that led here, as well as their pain points that both prevent moving and/or encourage moving. If Facebook suits the needs of the school and the majority of parents, stop being angry and realize that there's a value in the platform for the purpose.
How interesting that the Buttery Mails have really turned out to be his.