Currently users you block can still see your posts, reply to those posts, and trigger notifications when they do reply.
You can read the beginning of messages people you have blocked in your notifications tab, but have to unblock users to see the rest of what everyone else reading the replies to your post can see.
A “blocking” feature that is only inconvenient to the blocker is worse than no blocking feature at all, equivalent to trying to escape a fistfight by turning invisible but actually just closing your eyes.
If you’re having a conversation in a public space and a third party joins the conversation you can choose to walk away, but you don’t get to force anyone else to come with you - they get to decide for themself who they want to engage with.