it wouldn't be a very _good_ feature because if it was, because there are SO MANY INSTANCES. Blocking one large one is not going to stop anything, and there's no pattern to domains, and .... just no. I mean yes, you could go "oh this looks like a sub-url of a mastodon server let's block that but there's side-effects to that and also it's pretty easy for mastodon devs to circumvent