The new "Following" section has a plus (+) icon on top that shows who's on your list, so you can remove them if their pins don't seem relevant anymore. You can quickly replace the people you unfollow, though, because it also recommends users you can add based on your interests.

This new feature sounds especially useful if you couldn't be bothered to organize your boards -- the website recently rolled out a collection of useful organizational tools -- but can't bear to see all the clutter. You'll start seeing it today, no matter what device you're using, since it's rolling out on Android, iOS and the web.