> It seems every Mastodon instance is its own kingdom managed by people I don't know running on arbitrary rules they've set.
Yep! This is also exactly how e-mail works, and yet everyone manages to get an e-mail account (or ten) with no problems.
> I still gave their server browser a try, and couldn't find anything that looks remotely official on the first page.
"Hello, helpdesk? I can't find the official email server. No, not Hotmail, not Yahoo, not G-mail, not Apple Me. I only want the official email server. Hello?"
> tl;dr for now mastodon doesn't offer an easy path to just use the service w/o thinking about its details.
Sure it does? Pick a free+open provider to register yourself (or ask any of your friends for an invite to their server).
It's no more effort than say, signing up for a cellphone telephone number, and everyone figured out how to do that. Children manage to handle "you have to pick a server first" when they load up Minecraft (each of which has it's own moderators and their own unique rules! -- some are even invite-only!), and the kids seem to get along just fine.
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I get your point. Being a free, open, decentralized network means there's one extra step to registration -- I agree with your complaint.
But it's literally just one extra step, and it's not even a difficult one. The idea that this makes Mastodon difficult to use because of that, seems completely farfetched -- every other popular network has had a similar step and managed to overcome it with zero issues.