I think they should stick to the "email provider" analogy. Whole paragraph should be something like:
The only thing you need to start interacting with the Fediverse is an account with one of the many providers, just like with email! Providers are freely available across the globe: pick one that suits your location or interests best! You can start browsing the content of nearly the entire Fediverse from whatever provider you choose. Don't worry, you can always create an account with a different provider later.
You could add a sentence or two about where to find sensible defaults or link an article that explains the more subtle things.
I think the emphasis on instances (and not naming them the more familiar providers) hinders adoption.
That's a great analogy, but it's too big a barrier for many, most give up before picking a instance, we should set good defaults and then the users can figure it out once they are used to the platform.
Yes, very much in favor of sensible defaults for first timers. Most frontends/apps support multiple accounts anyway so changing/adding more later on really shouldn't be a problem
The difference is that the email provider you chose won't make it so you can't send an email to your friends because your providers don't talk to one another.
No, that's not true. The big email providers absolutely block smaller and personal hosts. There's a whole system of features and options you need to install and support in order to get through the door, thanks to spammers.
Well, it's meant as an introductory paragraph. I think such a general paragraph should not go to those lengths since the vast majority won't be facing that issue. Most large instances that you would recommend for first timers are federated well enough that at least the civilised part of Lemmy is very accessible. I think that with:
sensible defaults/suggestions
easy to understand intro
a help/link to a detailed article
you cover enough for users who can't be bothered, who want to be informed, and those who want to understand what's going on behind the scenes.