Well, ultimately mastodon/lemmy are hobbyist projects. They would naturally count as “provided as is, with no guarantees”.

I don’t know about Lemmy, but Mastodon the software project is most certainly not a hobbyist project, blowing it off as one is just tone deaf. It’s a real non-profit company with actual developers on an actual payroll. mastodon.social and .online are real expenses on the balance sheet of that non-profit. pawoo.net was started by pixiv, a for-profit company, but changed ownership several times and is now owned by Sujitech LLC (along with mstdn.jp and mastodon.cloud). The owner of misskey.io is also in the process of forming a company.

Yes, they are “provided as is, with no guarantees” but the people who run them are completely and sincerely invested in their sustainability as more than just hobby projects.

All big fediverse instances are funded by users.

This isn’t true for a lot of them if you actually take a look. Consider the top 10 instances according to https://fediverse.observer/list

• mstdn.jp, pawoo.net, mastodon.cloud are run out of pocket (by the same owner (!!!)).
• misskey.io is partially funded by ads., registrations from non-Japanese IPs were also closed shortly after the Musk takeover.
• Funding for mastodon.social and mastodon.online is co-mingled with the funding for Mastodon the software project
• baraag.net barely has the funds to secure enough capacity for the number of users it serves (registrations have been closed for the past year)
• The admin of mstdn.social was apparently short on rent this month? (!!!)
• daystorm and pravda don’t count because their numbers are spoofed
• mastodon.world and mas.to can count themselves as lucky enough to be truly user-funded and (seemingly?) sustainable.

OP may not be good at phrasing things, but their concerns are completely legitimate. Almost ALL of the biggest instances are unsustainable on their own or have had to make compromises in order to stay online.

Feeds/timelines are first-class citizens in the AT protocol and are decoupled from account hosting.

On Mastodon, your timelines are computed by the same server that hosts your data. Consequently, signing up to a server to have an account on the fediverse is the same thing as joining a community. You follow the servers rules and share the same local timeline as everyone else on that server.

On Bluesky, feeds are arbitrary, fungible and provided by any server, and it can be computed/curated/moderated however they like. So communities are “built” around feeds rather than around account hosting providers.

The AT protocol also has “real” account portability (though I have not seen this demonstrated in practice https://atproto.com/guides/overview#account-portability). On Mastodon, account “portability” is a delicate dance that requires the cooperation of both the origin and destination server.

Mastodon has something that Bluesky currently doesn’t: real federation. The Bluesky server that everyone signs up to doesn’t federate with anyone else, since the whole protocol is still a work-in-progress.

I was going to join calckey.social/firefish.social but I’m a little hesitant now because mastodon.art defederated with it, and I follow multiple accounts from that instance. The drama that always surrounds defederation is a fundamental design flaw in the Fediverse

mastodon.art is unfortunately run by a harebrained power mod. Their predecessor was much much better and more thoughtful in their use of moderation powers.