I agree with you that blocking domains isn’t a solid general-purpose anti-spam measure – it’s more for whacking the occasional “heavy hitter”.
It is entirely possible, though, to customise mail-receiver to do whatever additional pre-delivery filtering you need, such as running incoming messages through SpamAssassin or similar, since you have the entire Power of Postfix at your command. I’ve been considering building a “mail receiver 9001” that incorporates these sorts of things out of the box, but it’d need to be a sponsored effort, as I don’t personally have a need for it at present.