It currently depends on which client you're using. The devs are working on building it into the server side, but at least 'connect for lemmy' on android allows you to block instances yourself.

any time i see a weird gif reaction i just block.

it gets repetitive, but that's the way it is for now.

at some point i might just move away from shitjustworks to an instance that actually cares.

If you are on browser using unlock origin, you can use custom cosmetic filters like sh.itjust.works##div.post-listing:has-text(/hexbear.net/). Not perfect and does not hide comments, but I've been happy enough with just this.