Threads was preemptively shitlisted just for thinking of connecting to Fediverse, because a lot of instance admins are ActivityPub or Mastodon maximalists[0] and believed that everyone would just flock over to Threads immediately.
Then it was shitlisted again because Mark Zuckerberg started zucking on Trump, and decided to take their already threadbare moderation team and tie their hands further. This is a more practical concern as most Fedi admins do not have the time or ability to deal with one mega-instance that happens to be both indispensable and willing to flood everyone with garbage.
I could see Tumblr getting shitlisted purely on the grounds of "fuck Matt Mullenweg", because Fedi admins are also hilariously petty[1]. But in practice, "just link Tumblr up to Fedi" is going to be just as much of a problem as "just link Threads up to Fedi".
There's an underlying tension between the Fediverse's technical underpinnings - ActivityPub - and the community of Fediverse servers that use it. The technology wants to be widely adopted, but the community wants to be small enough to avoid harassment and attacks[2], and these are in conflict. The Fediverse's structure is already a lot more centralized than anyone would like to admit, and scaling the network makes this problem worse.
[0] As opposed to general enthusiasm for federated communications technologies. See also the pushback Cory Doctorow got for backing Free our Feeds, a plan to make good on BlueSky's currently vacuous federation promises.
[1] This is why I self-host Mastodon even though it's a total pain in the ass.
[2] Like that one time a bunch of Japanese skiddies decided to spam literally every server from whatever accounts they could register
The problem is that it is expensive. Even if you host on a cheap VPS and put your media on some object storage like Storj (~$4/TB/month), you are problably looking at a minimum of $20/month for the server. If you get for yourself, maybe your friends and stay under 50 users, fine.
If you get more than that then you'll need a beefier server, and if any of users follows lots of media-heavy accounts and does not set it up to delete old posts, your object storage will be full very quick.
I delete posts mirrored from other servers older than 90 days with a cron job. It has a command to do this.
But I am still not happy with the idea that we should be deleting data from the server just to keep it manageable. It reminds of the before Gmail where people would get 5MB quota of Yahoo Mail and would have to go around deleting stuff from their mailboxes every other month.
> The Fediverse's structure is already a lot more centralized than anyone would like to admit
Hi, I'm "anyone", and: no it isn't? Technically and philosophically, no it isn't. Large instances are not a failure of decentralisation, because as you evidently know, their existence does not preclude you or anyone else setting up a server and federating. There's no universe in which "scaling the network" reduces decentralisation, in fact it's the solution to the "fuck Matt Mullenweg" situation you speculate about. The less homogenous fedi admins become, the more the network is sustained by people who don't even know who he is. Your comment is rife with generalisations about the motivations of people on the fediverse, but it's far less monolithic than you think.