To point out that "the main lesson I wish developers (and especially Moxie) get to learn is the one that teaches them that centralized services are fragile, bound to fail and simply not worth the cost." has nothing to do with centralized or not. It's not a reason to do things one way or another. There has never been a large long running system, centralized or not, 500 page book or not, that hasn't had user downtime or didn't incur cost. This part is not a matter of theory nor what decentralized systems set out to solve.

There are other valid lessons for why choose decentralized but this is not a "ha, got'em" moment for that. There are also valid pros for centralized as well, hence their real world success and the reason most "decentralized" tech ends up being run in a very centralized fashion when it matures.