I imagine that's part of the motivation behind this decision.

For that I would recommend extensions like https://addons.mozilla.org/en-US/firefox/addon/news-feed-era... which clear the endless feed but still let you visit the site for messaging. You can probably also use uBlock Origin to do this if you don't want to install anything new.

The blast radius is more corporate and school networks that block facebook.com

how many people willing to update their hosts file to redirect internally so that you are still able to avoid typing facebook.com? If someone was willing to block the domain, I'm guessing a high percentage of those would be amenable.