I see it as follows:

There is a chance that if I post something from reddit / twitter / whatever, it gives room to talk about it to someone who would not otherwise have done it because those posts are there and not here (account blocked, deleted, shadowbanned, whatever).

So , to me, it largely depends on what is being reposted. Things like news, official service pages or software releases? Not really useful to mirror to the social networks, you could just link to the source (or a better one than nazi sites use). Cats? Beautiful! Linux? Absolutely! Antiworker life pro tips? Useful! Local stores that don’t have their own webpage but an Instagram instead? Eh, but OTOH how else, unless one of us is volunteering to host them one. Arts and crafts? Nice to have, but with the understanding that the OP won’t get to see our feedback; sometimes that’s fine, sometimes we want to talk about a thing and not to the thing.