The embrace/extend/extinguish arguments are all FUD arguments. Arguments 2 and 3 boil down to Threads effectively walling off their side, which would more or less mean de-federation. And what happens when your now free Lemmy instances starts requiring you to pay $8/month? Or what if some of the larger instances decide to commercialize and sell data? FUD is not a compelling argument: the same arguments were made about Microsoft and their open source embrace. And there are plenty of FUD arguments to make against Lemmy.
I would argue that federation with commercial entities will make for a better Fediverse. Sure Meta is subjectively Evil, but it's motives are clearer than some random dude's Lemmy instances. And by Federation there is ability to get high quality news, science and technology information. In less than a day, major players joined and were posting to Threads.
The email analogy is a false dichotomy. The reason behind the large email providers is because the cost of the running and maintaining an email server is cheaper than running your own. But you could run a trusted email service if you set up your DNS records correctly.
Take an upvote, but I think the situation I'd very different from the XMPP and the office standards or even kerberos. In each of those cases, it was a standard.
For the XMPP case, XMPP use for Google was primary business users. The XMPP case ignores the rise of other, more convient, more engaged communication like Facebook Messenger, discord and free text messaging. For the open standard of OOXML, Microsoft's aim was to sell Office. And for Kerberos, the AD changed were driven by business reasons. Regular kerberos is insane to admin, and Microsoft made it easy; it doesnt help that Novell's eDitectiry failed.
With Federation, the story is different. The engagement isn't like XMPP of connecting to people you know, or the security reasons of AD or even the standards of OOXML. In a sense, Federation is more like DNS or a web server: it's just about connecting communities.