(To my great disappointment, a lot of "how to self-host" guides just omit that step, and quietly assume that disks don't go bad...)
A poor haphazard backup is better than no backup.
but is it better than cloud provider?
Cloud provider can lock you out without recourse and you'll lose your data.
Local backups can fail, be destroyed (for example a failed PSU kills both your PC and any attached devices), or be deleted by malware
How complex do you need to have your local backup to achieve cloud providers' reliability?
So, keeping a half-assed backup copy on a spouse's machine in a different room is still better than not keeping any copy at all. It will not protect from every disaster, but it will protect against some.
My own backups progressed from manual rsync to syncthing to syncthing for every machine in the house + restic backups (which saved my bacon more than once).
Of course, lots of work was done in the background to reach this point, but I think it is possible. Will I make the effort to make that happen for a social network? No, because I am not using them that much.
Technically things become simpler (in the sense that you can do it "at home" and if you add LLM-s to answer you when you don't know some obscure option it is even easier), but identifying well the use-case, deciding defaults, writing documentation, juggling trade-offs will remain as hard as before.
Note/edit: something being possible does not mean one should do it, so I think it will depend on everybody's priorities and skills. I wish though good luck to anybody trying...