If you haven't joined the community, you should see this button to block it below where the Subscribe button is.
edit: Also, if you only want to see what you're subscribed to in your timeline, you can click on "Subscribed" where you see "Subscribed Local All" at the top of your timeline. Subscribed will show you communities you're subscribed to on all instances. Local will show posts from all communities only on your local instance, and All will show posts from all communities from all instances (at least, all instances that your local instance is federated with.)
edit 2: after typing that last edit, I see that the original question was asked 9 months ago. Oh well, maybe it's relevant for some of the new people joining.