"It's the only link that appears at the bottom of my emails."

Personally, I've noticed an increasing affinity for the 'tag as spam' button.

It takes a certain amount of effort to scroll down, and find the unsubscribe (I'm not even sure if it's there), vs. having my inbox cleaned up by just clicking the darn 'tag as spam' button -- dead easy. Also, there's the uncertainty about how daunting the unsubscribe experience might be. These days, quite many startups get their users to go through tedious surveys before they can unsubscribe completely. This results in a sticky association that's hard to undo: 'unsubscribe' is a hassle.

Are there ways around this?

How about a large button above the fold that says 'Don't mail me.', 'Junk!' or similar. Something that indicates they'll have their intended results: less of this sorta mail, and a cleaner inbox. On the other hand, this might result in more unsubscribes.